208 


HYDROELECTRIC  PLANTS. 


COSTS. 

Fig.  192  gives  the  cost  per  foot  of  reinforced  concrete  pen- 
stock. The  data  from  which  this  curve  is  plotted  was  derived 
largely  from  Gillette's  book,  "  Cost  Data,"  but  also  from 
numerous  other  sources. 


FIG.  191. 

Reinforcing  costs  about  three  cents  per  pound  for  steel, 
and  C.5  cent  to  instal.  The  concrete  costs  bout  $10.00 
per  cubic  yard,  including  every  item.  Round  rods  cost  about 


Gasfjoer/vof  of  Penstock 
FIG.  192. 


$34.00  per  ton.  Brick  penstocks  require  570  bricks  per  cubic 
yard  and  1.25  barrels  of  cement.  A  mason  should  lay  1200 
bricks  in  eight  hours  at  a  cost  of  $6.00 

Figs.  193  to  195  show  the  three  common  forms  of  steel  riveted 


HYDRAULIC  CONSTRUCTION. 


209 


PLANCED    ENTRANCE     TAPER 
BOLTED  TO  PRESSURE     BOX 


FIGS.  193-195. 


UNIVERSITY  OF  CALIFORNIA 

ANDREW 

SMITH 

HALLIDIE: 

1868^1  1901 


DESIGN  AND  CONSTRUCTION 

OF 

HYDROELECTRIC 
PLANTS 

INCLUDING    A    SPECIAL   TREATMENT 
OF  THE 

DESIGN   OF    DAMS 

BY 


R.  C.  BEARDSLEY 


NEW  YORK 

McGRAW  PUBLISHING  COMPANY 
1907 


|\\ 


Copyrighted,  1907, 

by  the 

McGraw  Publishing  Company, 
New  York. 


To  my  father,  E.  R.  Beardsley, 
to  whom  we  owe  the  gravity  dam, 
and  the  discovery  of  the  existence 
and  effects  of  vacuums  under  dams. 


' 


CONTENTS. 

CHAPTER.  PAGE. 

I.  HYDRAULIC  PRINCIPLES 1 

Hydrostatics 1 

Hydrodynamics 2 

II.  MEASUREMENT  OF  FLOW 10 

Weirs 10 

Dams 12 

Velocity  of  Approach 15 

The  Nappe 17 

Venturi  Meters 18 

Penstocks  and  Pipes 20 

Established  Values  of  n 22 

Circular  Penstocks 23 

Flow  in  Penstocks 25 

Short  Pipes 29 

Flow  of  Air  in  Pipes 30 

Limiting  Velocities  for  Air 30 

Canals 31 

Effect  of  Ice  on  the  Flow 32 

Rivers,  Preliminary  Measurements 33 

Current  Meters 35 

Extensive  Measurements 37 

III.  RECONNAISSANCE  OF  WATER  POWER 39 

Power  Measurement 39 

Value  of  Government  Reports  to  the  Hydraulic  En- 
gineer   40 

Relation  of  Pondage  and  Reservoirs  to  the  Valuation 

of  Power 45 

Penstock  with  Reservoir 51 

Ice  Evils 55 

Soundings 56 

Flowage  Height 58 

Cost  of  Surveys 61 

Engineer's  Report 62 

Engineer's  Measurements 62 

Form  of  Report 65 

IV.  MATERIALS 68 

Wood 68 

Metals 69 


vi  CONTENTS. 

CHAPTER,  PAGE. 

IV.  MATERIALS  (Continued). 

Cement  and  Concrete 69 

Testing 70 

Uses 85 

Sand  Cement 88 

Burnt  Clay  and  Gumbo 88 

Costs .  89 

Hand-Mixed  Concrete 90 

Machine  Mixed  Concrete 92 

Forms 94 

Surfacing 96 

Concrete  Laid  under  Water 98 

General  Remarks 99 

Peculiarities  of  Concrete 100 

Concrete-Steel 102 

Strength  of  Materials 113 

Columns  and  Foundations 122 

Design  of  Machine  Elements 130 

V.  HYDRAULIC  CONSTRUCTION 137 

Piling 137 

Drilling 149 

Explosives 155 

Cableways 159 

Bridges 164 

Coffer  Dams 169 

Caissons 175 

Costs 179 

Pumps 179 

Hydraulic  Ram 183 

Embankments 185 

Canals 187 

Tunnels 192 

Penstocks 199 

The  Design  of  Dams ". 210 

Costs 274 

Flashboards 281 

Head  Gates 289 

Sluice  Gates 296 

Head  Racks 298 

VI.  POWER  HOUSE  CONSTRUCTION 301 

Foundations 301 

Structure 303 

Architecture 330 

VII.  POWER  HOUSE  EQUIPMENT 331 

Waterwheels 331 

Hydro-Compressor 370 

Auxiliary  Plants 381 


CONTENTS.  vii 

CHAPTER.  PAGE. 

VII.  POWER  HOUSE  EQUIPMENT  (Continued). 

Electric  Generators 393 

Switch  Boards 398 

Switches  and  Instruments 402 

Lightning  Arresters 413 

Transformers 415 

Storage  Battery 421 

Motor  Generators 429 

Frequency  Changers 429 

Alignment  of  Machinery 43 1 

VIII.  POWER  TRANSMISSION 434 

Couplings 434 

Friction  Clutches 435 

Keys 436 

Quill  Shafts 436 

Shafting 436 

Gears .< 440 

Belting 446 

Rope  Transmission 449 

High  Tension  Electric  Transmission 460 

Efficiencies 486 

Efficiency  of  Old  Wheels 493 

IX.  TABLES  AND  FORMULAS 495 

Various  Units 495 

Power  and  Energy  and  Their  Equivalents 495 

Application  of  Energy  Formulas 496 

Comparison  of  the  Value  of  Power  when  Expressed 

in  Horse-Power  per  Year  or  Kilowatt  per  Year. .  501 


CHAPTER  I 
HYDRAULIC   PRINCIPLES. 

HYDROSTATICS. 

Water  is  chemically  known  as  H2O.  Its  weight  varies  from 
62.3  pounds  to  62.5  poi.nds  per  cubic  foot. 

In  all  estimates  on  water  power  the  value  should  be  used 
which  gives  results  on  the  safe  side.  Thus,  in  finding  the 
power  of  the  stream  62.3  should  be  used,  but  in  obtaining  the 
pressure  on  the  dam  or  against  a  gate,  62.5  is  the  safest  figure. 
In  turbine  testing,  where  great  accuracy  is  required,  the 
water  should  be  weighed  during  the  test. 

1  cubic  foot  of  water  =  6.232  imperial  gallons  =  7.48  United 
States  gallons. 

1  imperial  gallon  =  .1605  cubic  foot  =  1.2  United  States 
gallons. 

1  United  States  gallon  =  .1337  cubic  foot  =  .331  imperial 
gallons. 

1  United  States  gallon  =  8.355  pounds  =  231  cubic  inches. 

1  miners  inch  =  11.219  United  States  gallons  =1.5  cubic 
foot. 

The  miner's  inch  is  not  the  same  in  all  parts  of  the  country, 
but  the  value  given  above  is  becoming  universally  acknowledged. 
• x  ater  is  but  slightly  compressible,  therefore  the  pressure,  P, 
is  for  all  practical  purposes  directly  proportional  to  the  depth, 
H,  and  can  be  represented  by  a  diagram  as  shown  in  Figs.  1, 
2  and  3. 

The  total  pressure  on  any  submerged  surface  is  equal  to  the 
area  of  the  pressure  diagram  (a  b  c.  Fig.  1 ;  d  e  c  b,  Figs.  2  and 
3),  and  the  center  of  pressure  passes  through  its  center  of 
gravity  G  perpendicular  to  the  submerged  surface.  The 
moment  of  the  pressure  about  c  is 

M  =  Py. 
1 


2  HYDROELECTRIC  PLANTS. 

The  pressure  in  pounds  per  square  inch  at  any  point  is 
p  =  0.433  Depth. 

The  pressure  is  always  normal  to  the  submerged  surface 
(Fig.  4).  The  total  pressure  exerted  on  a  submerged  body  is 

P  =  0.433  H  S 

wherein  5  is  the  area  of  the  surface  and  H  the  depth  of  water 
over  the  geometrical  center  of  the  body. 

Any  body  submerged  in  water  will  suffer  an  apparent  loss  of 
weight  which  is  equal  to  the  weight  of  the  displaced  volume 
of  water.  If  a  unit  volume  of  water  is  heavier  than  a  unit 
volume  of  the  substance  the  latter  will  float. 


FIG.  1. 


FIG.  2. 


FIG.  4. 


HYDRODYNAMICS. 

Water  in  motion  is  governed  by  the  same  law  as  falling  bodies, 
i.e., 

m  v2 

mgh-  __. 

wherein  m  g  h  represents  the  potential  energy  due  to  its  position 


and 


m  v2 


represents    the    kinetic    energy    due    to    its    velocity. 


This  equation  holds  true  only  for  an  efficiency  of  100  per  cent. 


HYDRAULIC  PRINCIPLES. 


3 


The  quantities  which  enter  into  the  equation  are  the  mass, 
m,  head,  h,  velocity,  v,  and  the  gravity  constant,  g  =  32.16, 

m  g  =  w  =  weight 
and 


v  =  V2gh  =  8.03V  h 

When  h  is  given  in  feet,  v  is  the  velocity  in  feet  per  second. 

The  flow  of  water  through  an  opening  expressed  in  cubic  feet 
per  second  is 

Q  =  vA 

wherein  v  is  the  velocity  in  feet  per  second  and  A  is  the  area 
in  square  feet,  of  the  opening. 


FIG.  5. 

For  rectangular  openings  of  length,  /,  and  depth,  d,  the  for- 
mula for  Q  is 

Q  =  c  I  d  x/277*     (Fig.  5) 

For  circular  openings  of  diameter  d  the  formula  for  Q  is  (Fig.  5) 

_  ,12  /  1        M  £          ,74  \ 

Q  =  c^-V2gh    (1-JL1_-_J_^L_....) 
4  V        128  h2         16384  h4  / 

for  values  of  h  >  2  d 


'  Q-c-  .rv'2H 

wherein  <:  is  a  coefficient  which  depends  on  the  form  of  the  orifice 
and  may  be  taken  as  0.61  for  openings  in  thin  plates  or  planks 
such  as  head  gates;  Q  is  given  in  cubic  feet  per  second  when 
h.  I  and  d  are  measured  in  feet. 


4  HYDROELECTRIC  PLANTS. 

The  above  formulas  for  flow  through  orifices  supposed  that 
there  is  no  velocity  of  approach  and  are  correct  to  within  0.5 
per  cent,  when 

A   f 

^>  10 
A 

wherein  A'  is  the  area  of  cross-section  of  the  canal  or  tank  and 
A  that  of  the  orifice. 

When  , 


The  velocity  of  approach  should  be  taken  into  consideration. 
Let  h0  be  the  head  due  to  the  velocity  of  approach,  i.e., 


V 

^7 

T 
t 


FIG.  6. 


Then 
Q  =  c\ 


FIG.  7. 


c  --=  0.61 


FIG.  8. 


(Fig-  6. 


for  rectangular  openings  of  length  /. 

For  submerged  orifices  the  discharge  is  practically  the  same 
as  in  the  case  of  a  free  discharge  except  that  the  head,  h,  is 
taken  between  the  two  levels  (Fig.  7). 


Q  =  c  A  \/2  h  g 
c  =  0.6 

The  weir  is  a  special  case  of  a  rectangular  orifice  where  hl  =0. 

Q  =  §r/V2j(fe2  +  «fc0)!      (Fig.  8.) 

n  =--  1.0-  1.5         c  =  0.60 
Suppose  water   to  be    conducted    through   a   pipe     line    from 


HYDRAULIC  PRINCIPLES.  5 

one  reservoir  to  another.  The  difference  between  the  levels 
being  h  (Fig.  9).  If  pressure  tubes  are  inserted  at  intervals 
along  the  pipe  line  their  levels  will  coincide  with  the  line  a  b 
called  the  hydraulic  gradient  when  the  line  is  open  and  with  the 
line  a  a'  when  the  valve  at  B  is  closed.  This  reduction  in 
pressure  head  is  due  to  two  things,  namely,  frictibn  losses  and 
conversion  of  pressure  head  into  velocity  head.  The  velocity 
head  is  represented  by  hv  and 


FIG.  9. 


The  friction  head  lost  at  the  entrance  to  the  pipe  is  expressed 
thus 

C2g 
c  =  0.5  (approximately) 

The  friction  head  lost  in  the  pipe  is  directly  proportional  to 
the  length  of  the  pipe,  inversely  proportional  to  the  diameter 
of  the  pipe,  directl>  proportional  to  the  square  of  the  velocity 
and  is  expressed  thus 

/      I/2 
Cd     2f~ 

c  is  the  coefficient  of  friction . 


6  HYDROELECTRIC  PLANTS 

The  total  available  sta:ic  head  is 
h  =  hQ  +  hf  +  hv 

From  Figs.  9  and  10  it  is  seen  that  a  pipe  laid  along  the  hy- 
draulic gradient  would  not  be  subjected  to  pressure  except 
when  the  pipe  is  closed  at  the  lower  end  and  open  at  the  upper, 


FIG.  10. 


and  that  at  all  portions  of  the  pipe  line  which  lie  below  the 
hydraulic  gradient  are  subjected  to  the  pressure  hp  from  the 
inside  while  those  that  lie  above  it  are  subjected  to  the  pres- 


sure hp  from  the  outside. 


When  the  pipe  line  rises  above  the  hydraulic  gradient  it   is 


FIG.  11. 

called  a  siphon.  A  siphon  requires  an  air  tight  pipe  because 
its  operation  depends  upon  the  possibility  of  raising  the  hy- 
draulic gradient  by  an  amount  equal  to  the  head  due  to  the 
atmosphere  as  shown  in  Fig.  10.  Even  though  the  pipe  be 
air  tight  some  air  will  be  carried  in  by  the  water  and  will  collect 
in  the  pipe  at  the  highest  point.  At  this  point  a  tank  with 


HYDRAULIC  PRINCIPLES.  7 

a  valve  must  be  inserted  to  collect  and  carry  off  the  air.  It 
is  also  used  to  start  the  siphon.  The  operation  is  explained 
as  follows  (Fig.  11) : 

To  operate  the  pipe,  the  valves  at  B  and  C  are  closed,  D 
opened  and  the  whole  siphon  and  reservoir  E  filled  with  water. 
B  and  C  are  now  opened,  D  being  left  open.  Then, 
as  the  air  forms  during  the  operation  of  the  pipe,  the  air  drives 
the  water  out  of  E,  but  E  having  some  capacity,  it  requires 
time  to  do  this  and,  before  E  is  entirely  emptied,  the  valve  D 
is  closed  and  E  filled  with  water,  after  which  D  is  opened  again. 
In  this  way,  the  siphon  may  be  caused  to  operate  continuously. 

If  the  head  lost  by  friction  in  the  pipe  exceeds  20  to  25  feet 
the  pipe  will  not  operate  successfully. 

In  a  siphon,  the  pressure  to  be  contended  with  is  that  due 
to  air  pressure  and  the  pipe  must  be  strong  enough  against 
collapsing  to  stand  15  pounds  per  square  inch. 


FIG.  12. 

Siphons  may  form  a  part  of  the  penstock  when  it  is  cheaper 
than  tunnelling.  Large  siphons  may  be  built  of  wooden  staves 
though  riveted  steel  pipe  is,  in  all  cases,  preferable. 

From  Fig.  10  it  is  seen  that  the  hydraulic  gradient  is  raised 
by  an  amount  equal  to  the  head  due  to  the  atmospheric  pres- 
sure and  that  the  pipe  should  work  as  well  above  as  below  the 
apparent  hydraulic  gradient.  This  is  true  enough  in  theory,  but 
in  practice  pipes  will  leak  and  allow  air  to  enter  and  the  water  will 
carry  air  which  will  collect  at  the  high  points  and  form  air  plugs, 
and  shift  the  hydraulic  gradient  from  its  normal  position  to  that 
shown  in  Fig.  12,  so  that  the  part  of  the  pipe  above  the  point  C 
will  be  under  pressure  and  the  discharge  will  take  place  at  C, 
the  rest  of  the  pipe  acting  simply  as  a  channel  to  convey  the 
water  from  there  to  the  end.  This  will  cause  a  material  decrease 
in  the  velocity  and  consequently  the  flow  of  the  water.  Water 


8 


HYDROELECTRIC  PLANTS. 


carried  from  a  great  height  is  often  utilized  at  a  nozzle  by 
absorbing  its  kinetic  energy  as  in  a  Pelton  wheel.  In  this 
case  the  velocity  is  kept  low  in  the  pipe  so  as  to  reduce  the 
head  lost  in  friction  and  the  greater  part  of  velocity  head  de- 
veloped in  a  nozzle.  Fig.  13  shows  the  hydraulic  gradient 
for  a  case  of  this  sort.  In  the  cases  which  went  before,  the 
gradient  was  taken  as  a  straight  line  from  one  end  of  the  pipe 
line  to  the  other,  but  this  is  only  true  where  the  pipe  itself 
follows  approximately  a  straight  line  between  the  reservoir  and 
the  discharge. 

The  impulse  pressure  at  the  nozzle  is  obtained  by  assuming 
that  this  velocity  was  produced  by  the  action  of  a  force  F  for 
a  period  of  one  second;  then  the  product  of  the  force,  F,  and 

the  distance,  — ,   through  which  the  weight   W   moves  in   one 


FIG.  13. 
second,  is  the  work  and  is  equal  to  the  kinetic  energy,  thus 


.,.  V 

W  —  = 


V  V2  V2 

q  —  =  w  a  —  =  2w  a  — 


wherein  q  is  the  volume  per  second,  w  the  specific  weight  of 
water,  and  a  the  area  of  the  orifice.  Thus,  it  is  seen  that  were 
there  no  losses  the  head,  h,  corresponding  to  the  velocity,  v, 
would  produce  an  impulse  pressure  equal  to  that  produced  by 
a  static  head,  2  h.  This  demonstrates  that  the  sudden  closing 
of  a  valve  in  a  pipe  line  may  subject  the  pipe  to  enormous 
pressure. 


HYDRAULIC  PRINCIPLES.  •  u 

The  time,  T,  which  it  takes  the  water  to  attain  its  final  ve- 
locity in  a  frictionless  pipe  or  to  come  to  rest  when  a  valve 
is  closed  is, 

r  «•  0.249  vT  seconds, 

wherein  /  is  the  length  of  the  pipe  in  feet. 

The  kinetic  energy  in  foot  pounds  possessed  by  a  pipe  full 
of  water  in  motion  is, 

ER  =  0.765  d  I  v>  =  h 

=  49.2  J//* 

wherein  d  is  the  diameter  of  the  pipe  in  feet,  /  the  length  in 
feet,  h  the  head  in  feet,  and  v  the  velocity  in  feet  per  second. 


CHAPTER  II. 
MEASUREMENT  OF  FLOW 

The  flow  is  the  amount  of  water  which  passes  a  given  point 
in  a  given  time,  and  is  determined  by  substituting  experimental 
constants  in  theoretical  formulas  which  are  derived  for  the 
aperture  through  which  it  is  desired  to  measure  the  flow. 

WEIRS. 

Weirs  are  used  in  measuring  the  flow  in  small  streams  or 
the  discharge  of  turbines,  pumps,  etc. 


FIG.  14. — Wire  for  small  streams. 

The  author  has  found  that  the  construction  shown  in  Fig.  14 
is  very  satisfactory  when  the  flow  of  small  streams  is  to  be 
measured.  The  weir  may  be  of  any  length  or  si?e,  and  built 
on  any  bottom  and  is  easily  and  quickly  constructed  in  swift 
water. 

10 


MEASUREMENT  OF  FLOW. 


11 


The  posts,  .4,  are  driven  with  a  maul  at  equal  distances  apart 
across  the  stream  and  as  nearly  as  possible  in  line. 

Then  the  floor  is  made  on  shore,  in  sections  of,  say,  12  feet  in 
length  and  as  wide  as  thought  necessary,  for  that  particular 
bottom  and  height  of  weir.  Holes  are  cut  in  the  floor  so  that 
it  may  be  dropped  down  over  the  posts. 

The  sections  are  then  placed  over  the  posts  and  sunk  on  to 
the  bed  of  the  stream  and  weighted  down  with  rock.  The 
tops  of  the  posts  are  cut  tapering  and  all  on  the  same  level 
except  the  four  end  posts  which  are  left  long  to  form  the  abut- 
ments. Then  the  first  plank,  E,  is  fitted  to  the  floor  so  that 
its  upper  edge  is  perfectly  level.  If  the  river  bed  is  of  sand  a 
row  of  sheet  piling  must  be  driven  at  C  before  the  floor  or 
mat  is  placed,  but  for  most  bottoms  this  will  not  be  necessary. 
Having  placed  the  plank,  E,  fill  above  it  with  earth  to  prevent 
the  water  cutting  under  the  floor  when  the  head  is  increased. 


FIG.  15. 


FIG.  15a. 


The  height  of  these  planks  will  depend  on  the  depth  of  the  water 
as  the  top  or  weir  plank  must  be  at  least  a  foot  above  the  lower 
water  level.  Champfer  the  edge  of  the  weir  plank,  B,  to  a  thin 
edge,  and  place  plenty  of  earth  at  the  ends.  A  stake,  D,  is 
driven  up  stream  a  distance  of  six  feet  or  more  from  the  we  r 
so  that  its  top  is  exactly  on  a  level  with  the  top  edge  of  the 
weir  plank. 

The  total  cubic  feet  of  water  per  minute  flowing  in  the 
stream  is  obtained  by  measuring  the  depth  of  water  over  the 
stake,  D,  and  from  the  weir  table  (see  Table  II)  finding  the 
cubic  feet  of  water  flowing  each  minute  per  foot  width  of  weir 
then  multiplying  this  quantity  by  the  width  of  the  weir  in  feet. 
Since  a  cubic  foot  of  water  weighs  62.5  pounds,  the  pounds  of 
water  flowing  per  minute  are  equal  to  the  flow  in  cubic  feet  per 
minute,  times  62.5. 

A  formula  which  takes  end  contraction  into  account  is  as 
follows : 


12  HYDROELECTRIC  PLANTS. 

Q,  the  cubic  feet  of  water  flowing  over  the  weir  per  min- 
ute =  199.8  (L  -0.1  n  D)  D  3/2. 

D  =  depth  of  water  in  feet  above  A ,  measured  at  a  point 
some  six  feet  to  ten  feet  up  stream  from  the  weir,  n  =  the 
number  of  end  contractions.  Thus  in  Fig.  15a  at  B,  n  =  0,  at 
C,  n=  1,  and  at  D,  n  =  2;  for  n  =  0,  the  formula  is,  Q  =  199.8 
LD3/2. 

Frequently  it  is  of  advantage  to  have  the  weir  plank  B  below 
the  lower  water  level,  in  which  case  the  weir  is  called  a  sub- 
merged weir.  In  this  case  the  depths  h  and  H  are  measured 
but  instead  of  referring  to  the  table,  substitute  these  measure- 
ments in  the  following  equation: 

Q  =  (Q  x  (width  of  weir  in  feet)  X  (8.025  \/a)  X  (h  +  f  a),  in 

TABLE  I. 
h/H  C 

.20 618  to  .628 

.40 590  to  .600 

.60 583  to  .593 

.70 580  to  .590 

.80 581  to  .591 

.90 590  to  .600 

.95 610  to  .615 

which  Q  =•  cubic  feet  of  water  per  second,  a  =  H-h,  and  C  is 
a  coefficient  depending  on  h+H  (see  Table  I). 

DAMS. 

While  the  flow  over  the  standard  weir  can  be  obtained  from 
Table  II,  which  is  based  on  Francis'  formula,  it  has  been  found 
that  for  the  forms  of  crest  found  on  power  dams  the  flow  varies 
a  good  deal  from  that  for  the  sharp  crested  weir.  The  experi- 
ments made  at  Cornell  are  the  latest  and  best  data  we  have 
on  the  subject,  and  Figs.  16  to  21  give  the  coefficients  C  for  six 
different  dams  and  for  depths  of  water  up  to  six  feet  as  given  by 
these  experiments. 

It  will  be  seen  that  the  coefficient  C  varies  considerably  from 
3.33  as  used  in  the  Francis  formula. 

EXAMPLE: — If  the  depth  of  water  on  a  dam  230  feet  long, 


MEASUREMENT  OF  FLOW. 


13 


TABLE  II. 

WEIR  TABLE  USING  FRANCIS'  FORMULA  Q  -  3.33 1  Kf. 
Discharge  in  cubic  feet  per  minute  per  foot  length  of  Weir. 


ead  H 

in 

s.     ft. 

Cu.  ft. 
per  min. 

Head  H 

Cu.  ft. 
per  min 

Head  H 

Cu.  ft. 
per  min. 

Head  H 

Cu.  ft. 

per  min. 

HeadH 

Cu.  ft. 

per  min. 

In 
Ins. 

in 
ft. 

In 
Ins 

in 
ft. 

In 
Ins. 

In 

ft. 

In 

Ins. 

In 
ft. 

01 

.18 

7 

.58 

88.26 

13 

i 

1.15 

246.42 

20f 

1.72 

450.72 

27A 

2.29 

692.40 

.02 

.54 

7A 

.59 

90.54 

13 

10 

1  .16 

249.60 

20  'i 

1.73 

454.62 

271 

2.30 

696.90 

.03 

1.02 

7A 

.60 

92.88 

14 

1J 

1.17 

252.84 

20  J 

1.74 

458.58 

27$ 

2.31 

701.46 

04 

1.62 

7  A 

.61 

95.16 

14 

r 

1  .18 

256.08 

> 

1.75 

462.54 

27  H 

2.32 

706.02 

j      .05 

2.22 

7? 

.62 

97.56 

14 

i 

1  .19 

259.38 

> 

1.76 

466.50 

28 

2.33 

710.58 

06 

2.94 

7  re 

.63 

99.90 

14 

i 

1.20 

262.62 

2 

1.77 

470.52 

28  1 

2.34 

715.20 

H  -07 

3.72 

711 
1  6 

.64 

102.30 

14 

v 

1.21 

265.92 

2 

1.78 

474.48 

2.35 

719.76 

TJ  .08 

4.50 

7  *  3 

.65 

104.70 

14 

i 

1  .22 

269.22 

2 

1.79 

478.50 

28  A 

2.36 

724.38 

ft    09 

5.40 

71 

.66 

107.16 

14 

i 

1.23 

272.58 

2 

1.80 

482.52 

28  A 

2.37 

729.00 

ft  .10 

6.30 

8 

.67 

109.56 

14 

\ 

1  .24 

275.88 

2 

1.81 

486.54 

28,96 

2.38 

733.62 

7.26 

8| 

.68 

112.02 

15 

1.25 

279.24 

2 

1.82 

490.56 

28  H 

2.39 

738.24 

A  :i2 

8.23 

8J 

.69 

114.54 

If) 

1.26 

282.60 

22 

1.83 

494.64 

28  1| 

2.40 

742.86 

i     -13 

9.36 

8| 

.70 

117.03 

L5 

1  .27 

285.96 

22J 

1  .84 

498.66 

28  it 

2.41 

747.54 

\     -14 

10.44 

.71 

119.52 

15 

1.28 

289.32 

22  A 

1.85 

502.74 

29  A 

2.42 

752.16 

.15 

11.58 

81 

.72 

122.04 

15 

1  .29 

292.74 

22  A 

1  .86 

506.82 

29  A 

2.43 

756.84 

H  .16 

12.78 

8i 

.73 

124.62 

5 

1.30 

296.16 

22  A 

1.87 

510.90 

29J 

2.44 

761.52 

A  -17 

13.98 

8| 

.74 

127.23 

5 

1  .31 

299.58 

22  v». 

1.88 

515.04 

29i 

2.45 

766.20 

.18 

15.24 

9* 

.75 

129.73 

.->' 

• 

1.32 

303  .00 

22  H 

1.89 

519.12 

29^ 

2.46 

770.88 

.19 

16.56 

.76 

132.36 

i; 

I  .33 

306.48 

22  t? 

1.90 

523.26 

29  j 

2.47 

775.62 

.20 

17.88 

gi 

.77 

135.53 

IK 

1.34 

309  .90 

22  1  i 

1.91 

527.40 

29: 

2.48 

780.30 

.21 

19.20 

9i 

.78 

137.64 

6 

1  .35 

313.38 

23 

1.92 

531  .54 

29 

2.49 

785.04 

.22 

20.64 

.79 

143.23 

H 

'<f 

1.36 

316.86 

23  J 

1.93 

535.74 

30 

2.50 

789.78 

.23 

22.02 

SI 

.83 

142.93 

8 

\. 

1.37 

320  .  40 

23J 

1.94 

539.88 

30  i 

2.51 

.24 

23.52 

i] 

.81 

145.63 

i) 

•'( 

L.33 

323  .88 

230 

1.95 

544.08 

30J 

2.52 

.25 

24.96 

.82 

143.33 

6 

I 

1.39 

327.42 

23 

1.96 

548.28 

.26 

26.46 

ios 

.83 

151.03 

6 

1 

' 

1  .40 

330.96 

23 

1.97 

552.48 

.27 

23.02 

10£ 

.84 

153.84 

H 

1  .41 

334.50 

23; 

1.S8 

556.68 

.23 

29.58 

10* 

.85 

156.63 

7 

c 

1  .42 

338.10 

23; 

.99 

560.88 

.29 

31.20 

10  A 

.86 

159.36 

7 

<„ 

1.43 

341  .64 

24 

.00 

564  .  1  4 

.30 

32.82 

[0  A 

.87 

162.12 

7 

1  .44 

345.24 

24  J 

.01 

569.34 

.31 

34.50 

[0  A 

.83 

164.94 

7; 

1  .45 

348.84 

24i 

.02 

573.60 

M  .32 

36.18 

10  H 

.89 

167.76 

7 

1  .46 

352.50 

24| 

.03 

577.86 

.33 

37.86 

[0  f-| 

.90 

170.53 

7: 

1.47 

356.10 

24i 

.04 

582.18 

8l     -34 

39.60 

[0  ff 

.91 

173.46 

7 

1.48 

359.76 

245 

.05 

586  .  44 

k     .35 

41.40 

11 

.92 

176.34 

17 

1  .49 

363.42 

24? 

.06 

590.76 

A  -36 

43.14 

111 

.93 

179.22 

1S 

1  .50 

367.08 

24^ 

.07 

595.02 

ft  .37 

44.94 

111 

.•04 

182.10 

IS 

I  .51 

370.74 

24  1 

.08 

599.34 

A  .38 

46.81 

Hi 

.95 

184.93 

IS 

1  .52 

374.40 

25  A 

.09 

603.72 

H  -39 

48.66 

111 

.96 

187.92 

IS 

1  .53 

378.12 

25  A 

.10 

608.04 

\i  -40 

50.52 

111 

.97     190.86 

IS 

1  .54 

381  .84 

25  A 

.11 

612.36 

H  -41 

52.44 

111 

.98 

193.86 

IS 

1.55 

385.56 

25  * 

.12 

616.74 

A  -42 

54.36 

111 

.99 

196.80 

18 

I  .56 

389.28 

25| 

.13 

621.12 

A  -43 

56.34 

12 

.00 

199.80 

18  H 

1  .57 

393.06 

.14 

625.50 

k     -44 

58.32 

12£ 

.01 

202.80 

19 

1.58 

396.78 

253 

.15 

629.88 

.45 

60.30 

.02 

205.80 

19A 

.59 

400.56 

25  ii 

.16 

634.26 

• 

.46 

62.34 

12| 

.03 

208.86 

19 

;\ 

.60 

404.34 

26  A 

.17 

638.70 

.47 

64.38 

12i 

.04 

211.92 

19 

A 

.61 

408.18 

.18 

643.08 

.48 
.49 
.50 
£     .51 

66.42 
68.52 
70.62 

72.78 

121 

12! 

12M 

12  H 

.05 
.06 
.07 
.08 

214.98 
218.04 
221  .16 
224.22 

19A 
19^ 

19  ]-, 

i9fi 

.62 
.63 
.64 
.65 

411  .96 
415.80 
419.64 
423.48 

26  1 
26| 

26? 

.19 
.20 
.21 

.22 

647.52 
651  .96 
656.40 
660.90 

.52 

74.34 

13A 

.09 

227.40 

19| 

.66 

427.32 

26  1 

.23 

665.34 

1     -53 

77.10 

.10 

230.52 

20 

.67 

431.22 

26J 

.24 

669.84 

*     .54 

79.26 

13A 

.11 

233.64 

20 

i 

.68 

435.06 

27 

.25 

674.34 

i     .55 

81.48 

13* 

.12 

236.82 

20 

I 

.69 

438.96 

27  J 

.26 

678.84 

!     .56 

83.70 

134 

.13 

•240.00 

20 

.70 

442.86 

27  i 

.27 

683.34 

H  -57 

85.98 

.14 

243.18 

20 

I 

.71 

446.76 

27  § 

.28 

687.84 

14 


HYDROELECTRIC  PLANTS. 


^.8 


Depth  of  water  in  ft.  over  crest 

*   Rounding  corner  is  equivalent  to  an  increase  of  H=0.7  R, 
FIGS.  16  to  21. — Cornell  Experiments. 


MEASUREMENT  OF  FLOW. 


io 


of  section  shown  in  Fig.  18,  is  five  feet,  what  will  be  the  quantity 
of  water  passing  over  the  dam? 

For  h  =  5  we  find  that  C  =  3.7 
Q  =  Clhl=  3.7X230X51 

51  =  v/53  =  11.18  and  Q  =  9514    cubic    feet    per  second. 

Francis'  constant,  3.33,  would  only  have  given  8571  cubic 
feet  per  second. 

Fig.  22,  from  Cornell  experiments  shows  the  form  taken  by 
the  top  surface  of  the  water  flowing  over  four  different  dam 
crests  and  in  depths  up  to  six  feet. 

Fig.  23  shows  the  under  and  outer  surface  of  the  water  pouring 


FIG.  22. — Form  taken  by  water  passing  over  a  dam  (Cornell). 

over  the  dam  shown  and  plotted  from  measurements  made  by 
the  author  under  a  gravity  dam  at  Waldron,  111.  During  these 
experiments  it  was  observed  that  there  was  a  very  strong 
current  as  indicated  at  x. 

VELOCITY  OF  APPROACH. 

In  most  cases  met  with  in  actual  practice,  the  water  ap- 
proaches the  dam  with  a  greater  velocity  than  that  where  the 
formulas  here  given  were  evolved,  therefore  such  velocity 
must  be  allowed  for  in  applying  the  formulas. 

Let  H  be  the  true  head  of  water  on  the  dam  (Fig.  24) ;  h  =  the 
observed  head  at  a  distance  of  six  or  ten  feet  above  the  dam; 
Q-,  =  discharge  over  the  dam  due  to  the  head  h  in  cubic  feet 


16 


HYDROELECTRIC  PLANTS. 


per  second  per  foot  width  of  weir. ;  Q  =  discharge  due  to  the 
head  H;  v  =  velocity  of  approach  in  feet  per  second. 


»-  x/64.4~(H-fc)  -.7- 


Then 


"  H  ~  h  =I  6?~4  " 


Fig   24.)     (1) 


PIG.  23. — Form  taken  by  water  passing  over  a  darn  (Beardsley). 


FIG.  24. 

To  apply  these  formulas    obtain  Q  from  the  discharge  for- 
mula, Q  =  C  lk\,  and  substitute  for  Q  in   (1).     This  gives  an 

v2 

approximate    value    for    v,    which    substituted    in    =  Hv 

64.4 

gives  the  approximate  velocity  head,  Hv.     Then  Hv  +h  =  H, 
gives  a  close  approximation  to  the  true  head,  H,  from  which 


MEASUREMENT  OF  FLOW.  17 

by  again  substituting  in  the  formula  for  flow  in  cubic  feet  per 
second,   a  more  nearly   exact   value   for  Q   can   be   found.     If 
till  greater  accuracy  is  desired  the  process  may  be  gone  through 
again. 

Where  possible  the  value  of  v  should  be  determined  with  a 

meter  and  substituted  direct  in =  H. 

64.4 

THE  NAPPE. 

In  discussing  the  flow  over  dams  much  is  said  about  this 
and  that  form  of  nappe.  Nappe  is  the  name  given  to  that 
part  of  the  crest  of  the  dam  which  is  in  direct  contact  with  the 
water.  The  various  forms  of  nappe  are  as  follows: 

Depressed,  wetted,  adhering  and  free. 

A  depressed  nappe  is  due  to  the  formation  of  a  vacuum; 
the  sheet  of  water  is  more  or  less  pressed  in  upon  the  crest. 

An  adhering  nappe  is  partly  caused  by  the  vacuum  but  ap- 
plies to  all  cases  where  there  is  no  air  at  all  between  the  water 
and  the  crest. 

Wetted  nappe  is  where  the  air  has  free  access  behind  the  over- 
pour  and  the  crest  is  smooth. 

Free  nappe  is  where  there  is  no  vacuum  at  all. 

The  effect  on  the  coefficient  C  of  the  different  nappes  on  the 
same  dam  is  shown  by  the  following  experiment  on  a  short  low 
dam.  Q 

(1)  Free  nappe,  under  surface  open  to  air 4 . 33 — 3 . 47 

(2)  Depressed  nappe,  imprisoning  a  certain  amount 

of  air  at  a  pressure  below  normal 4 . 60 — 3 . 69 

(3)  Nappe  wetted,  no  air  imprisoned;  level  of  tail 

water  at  least  4.2  feet  below  level  of  crest ....  4 . 97 — 3 . 99 

(4)  Adhering  nappe .  .  .  5 . 54 — 4 . 45 

These  experiments  would  show  a  variation  of  20  per  cent., 
but  as  they  were  for  a  low  and  short  dam,  and  as  all  peculiari- 
ties tend  to  disappear  for  h^avy  discharges,  in  practice  the 
difference  would  not  be  so  noticeable. 

The  curves  for  the  six  dams  in  the  Cornell  experiments  are 
plotted  for  free  nappes. 

It  will  be  seen  that  the  gravity  dam  will  pass  more  water 


18  HYDROELECTRIC  PLANTS. 

for  a  given  depth  of  water  on  the  crest  than  will  a  thin  edged 
weir,  or  any  other  form  of  dam. 

VENTURI  METERS. 

Next  to  the  standard  weir,  the  Venturi  meter  is  the  most 
important  aid  in  the  measurement  of  water,  and  when  properly 
installed  and  calibrated  it  excels  the  weir  in  accuracy. 

Many  of  the  largest  cities  of  the  country  are  using  Venturi 
meters  to  measure  the  flow  of  water  in  the  water  systems,  and 
in  a  few  instances  such  meters  are  being  used  to  measure  the 
flow  to  turbines.  About  1887,  Mr.  Clemens  Herschel  brought 
the  Venturi  to  the  attention  of  American  engineers  and  since 
that  time  it  has  been  steadily  growing  in  favor. 

Fig.  25  shows  the  proportions  (all  dimensions  in  feet)  for 
the  Venturi  meter  used  by  Mr.  Herschel.  When  used  for 


FIG.  25. 

head  gates,  however,    (see  Fig.   26)    the  meter  may  be  mate- 
rially shortened. 

Fig.  26  shows  the  Venturi  meter  for  measuring  the  flow 
to  a  turbine  serving  the  double  purpose  of  a  meter  and 
a  head  gate.  Mr.  Herschel  states  that  a  Venturi  meter 
placed  in  a  nine-foot  penstock  in  which  the  mean  velocity 
is  about  '2.5  to  three  feet  per  second,  the  total  loss  in  head  will 
be  one  foot  and  if  the  velocity  is  two  feet  per  second  the  loss 
will  be  only  six  inches.  Therefore  in  all  but  water  powers  of  the 
lowest  head  the  Venturi  meter  can  be  used  to  measure  the  water. 
Since  it  does  not  affect  the  accuracy  of  the  meter  if  the  cones, 
a  and  b  (Fig.  25),  are  rough,  these  parts  may  be  constructed 
of  reinforced  concrete.  It  is  essential,  however,  that  the  throat 
c  be  made  accurately  and  of  metal  lined  with  bronze  or  brass. 
The  Builders'  Iron  Foundry  of  Providence,  R.  I.,  make  a  spe- 
cialty of  Venturi  meters.  The  air  chambers  D  and  E,  Fig.  26, 


MEASUREMENT  OF  FLOW. 


19 


must  also  be  of  metal.  Fig.  27  shows  one  form  of  air  chamber. 
The  effect  would,  however,  be  just  as  satisfactory  if  the  air 
space  was  not  divided  into  segments  and  if  but  a  single  pipe 
was  inserted  at  the  top. 

About  the  only  condition  that  effects  the  efficiency  of  the 
Venturi  is  the  falling  off  in  the  velocity  of  the  water  when  the 
demand  is  low.  This  would  not  be  an  objection  where  used  for 
turbines,  as  the  flow  would  never  be  below  about  20  per  cent,  of 
the  full  flow.  Mr.  Frizell  states  that  the  area  at  the  throat  must 
be  more  than  1/16  to  1/20  of  the  area  of  the  penstock  at  C 
Fig.  26,  in  order  that  the  meter  should  accurately  measure 


FIG.  26. — Venturi  meter  used  as  a  head  gate. 

the  flow.  Herschel  says  that  the  velocity  through  the  throat 
must  not  be  less  than  five  feet  per  second.  This  limits  the 
shortening  of  the  meter  as  the  taper  of  the  cones  meeting  at 
the  throat  must  be  as  given  in  Fig.  25.  When  used  for  head 
gates,  as  in  Fig.  26,  several  Venturi  meters  should  be  placed 
side  by  side,  in  wnich  case  if  all  the  turbines  are  running  at 
part  gate,  one  or  more  meters  can  be  cut  out  and  the  remaining 
meters  used  to  their  full  capacity  and  efficiency.  When  so 
arranged  the  meters  may  be  made  comparatively  short.  Noth- 
ing can  clog  up  a  Venturi  meter  even  saw  logs  will  be  metered  as 
water.  Mr.  Herschel  claims  that  the  Venturi  meter  is  accu- 
rate to  within  about  two  per  cent. 


20 


HYDROELECTRIC  PLANTS 


The  pipes  A  and  B,  Fig.  26,  lead  up  to  the  indicating  in- 
strument F.  This  instrument  is  made  in  various  forms  by  the 
Builders'  Iron  Foundry  and  gives  the  flow  in  cubic  feet  per 
minute. 

PENSTOCKS  AND  PIPES. 

We  are  indebted  to  Kutter  and  D'Arcy  for  our  most  reliable 
data  on  the  flow  of  water  through  pipes;  they  performed  many 
experiments  with  pipes  of  various  sizes  and  lengths,  and  their 
formulas  may  be  depended  on  as  being  exact  to  within  five 
per  cent.  We  will  only  give  one  formula,  and  the  accompanying 
tables,  the  author's  purpose  being  to  give  only  the  best  and 
easiest,  rather  than  to  give  a  variety. 


FIG.  27 

Q  =  A  C^XVs     v  -  CVTs  =  C  x/r  XV?7 

v  =  velocity  of  water  in  feet  per  second. 

A  ==  wet  area  of  penstock  =96,  Fig.  29. 

C  =  a  coefficient  depending  on  s,  n,  r , 

5  =  the   fall    of  water   surface    per    foot    length    or  hydraulic 

gradient 

fall  in  feet   per  mile 
5280 

^ 

r  =  —  =  mean  hydraulic  depth, 

P  =  wetted   perimeter  (see  Figs.  28-30). 


MEASUREMENT  OF  FLOW. 


21 


TABLE  III  (Kent). 

Q  —  discharge  in  cubic  feet  per  second,  -4=  area  in  square  feet,  v  =  velocity    in  feet 
per  second,  r  =  mean  hydraulic  depth,  i  diam.  for  pipes  running  full,  *  =  sine  of   slope. 


Size  of  Pipe 

Clean  Cast-iron 

Old  Cast-iron  Pipes 

Pipes. 

Value  of 

Lined  w  th  Deposit. 

A  C>/Fby 

A=  area 

Kutter's 

</  =  diam. 

in 

For 

For  Dis- 

Formula, 

For 

For 

in 
ft.       in. 

square 
feet. 

Velocity, 

c  vTT 

charge. 
AC^ 

when 
»  =  .013. 

Velocity. 

Discharge 
AC^/r- 

f 

.00077 

5.251 

.00403 

3.532 

.00272 

1 

.00136 

6.702 

.00914 

4.507 

.00613 

a 

.00307 

9.309 

.02855 

6.261 

.01922 

1 

.00545 

11.61 

.06334 

7.811 

.04257 

11 

.00852 

13.68 

.11659 

9.255 

.07885 

if 

.01227 

15.58 

.19115 

10.48 

.12855 

If 

.01670 

17.32 

.28936 

11.65 

.  19462 

2 

.02182 

18.96 

.41357 

12.75 

.27824 

2* 

.0341 

21.94 

.  74786 

14.76 

.50321 

3 

.0491 

24.63 

1  .2089 

16.56 

.81333 

4 

.0873 

29.37 

2.5630 

19.75 

1  .7246 

5 

.136 

33.54 

4.5610 

22.56 

3.0681 

6 

.196 

37.28 

7.3068 

4.822 

25.07 

4.9147 

7 

.267 

40.65 

10.852 

27.34 

7.2995 

8 

.349 

43.75 

15.270 

29.43 

10.271 

9 

.442 

46.73 

20.652 

15.03 

31.42 

13.891 

10 

.545 

49.45 

26.952 

33.26 

18.129 

11 

.660 

52.16 

34.428 

35.09 

23.158 

.785 

54.05 

42.918 

33.50 

36.75 

28.867 

2 

1.000 

59.34 

63.435 

39.91 

42.668 

4 

1.396 

63.67 

88.886 

42.83 

59.788 

6 

1.767 

67.75 

119.72 

102.14 

45.57 

80.531 

8 

2.182 

71.71 

156.46 

48.34 

105.25 

10 

2.640. 

75.32 

198  .83 

50.658 

133.74 

2 

3.142 

78.80 

247.57 

224.63 

52.961 

166.41 

2          2 

3.687 

82.15 

302.90 

55.258 

203.74 

2          4 

4.276 

85.39 

365  .  14 

57.436 

245.60 

2         6 

4.909 

88.39 

433.92 

411.37 

59.455 

291  .87 

2         8 

5.585 

91.51 

511.10 

61.55 

343.8 

2        10 

6.305 

94.40 

595.17 

63.49 

400.3 

3 

7.068 

97.17 

686.76 

674.09 

65.35 

461  .9 

3         2 

7.875 

99.93 

786.94 

67.21 

529.3 

3         4 

8.726 

102.6 

895.7 

69. 

602. 

3         6 

9.621 

105.1 

1011.2 

1021  .  1 

70.70 

680.2 

3         8 

10.559 

107.6 

1136.5 

72.40 

764.5 

3       10 

11.541 

110.2 

1271.4 

74.10 

855.2 

4 

12.566 

112.6 

1414.7 

1463.9 

75.73 

951.6 

4         3 

14.186 

116.1 

1647.6 

78.12 

1108.2 

4         6 

15.904 

119.6 

1901  .9 

2007. 

80.43 

1279.2 

4         9 

17.721 

122.8 

2176.1 

82.20 

1456.8 

5 

19.635 

126.1 

2476.4 

2659. 

84.83 

1665.7 

5         3 

21.648 

129.3 

2799.7 

86.99 

1883.2 

5         6 

23.758 

132.4 

3146.3 

3429. 

89.07 

2116.2 

5         9 

25.967 

135.4 

3516. 

91.08 

2365. 

6 

28.274 

138.4 

3912.8 

4322  . 

93.08 

2631.7 

6          6 

33.183 

144.1 

4782  .  1 

5339  . 

96.93 

3216.4 

7 

38.485 

149.6 

5757.5 

6510. 

100.61 

3872.5 

7         6 

44.179 

154.9 

6841.6 

7814. 

104.11 

4601  .9 

8 

50.266 

160. 

8043. 

9272. 

107.61 

5409.9 

8          6 

56.745 

165. 

9364.7 

10889. 

111. 

6299  .  1 

9 

63.617 

169.8 

10804. 

12663. 

114.2 

7267.3 

9          6 

70.882 

174.5 

12370. 

1  4597  . 

117.4 

8320.6 

10 

78.540 

179.1 

14066. 

16709. 

120.4 

9460.9 

22 


HYDROELECTRIC  PLANTS 


n  =  the  coefficient  of  roughness. 
Q  =  cubic  feet  of  water  per  second 


r  in    Fig.  28 


r  in  Fig.  29    = 


6X12 
6+12  +  6 

8X12 

8+12  +  8+12 


ESTABLISHED  VALUES  OP  n. 

In  all  formulas  for  flow  of  water  in  penstocks  the  one  un- 
certain factor  is  n',  the  value  of  n  for  any  particular  pipe  must 
be  guessed  at  before  the  capacity  of  the  pipe  can  be  deter- 
mined. The  following  will  be  useful  in  forming  a  close  guess. 
It  is  always  the  best  policy  to  take  the  next  higher  coefficient 
than  the  one  which  seems  to  fit  the  case. 


FIG.  28. 


FIG.  29. 


FIG.  30. 


n  —.01:  This  value  has  usually  been  used  for  wood  stave 
pipes,  concrete,  etc.,  but  has  been  found  too  small  in  practice. 

n  =  .012:  plaster  of  pure  cement;  planed  timber,  glazed, 
coated  or  enameled  stoneware  and  iron  pipes ;  glazed  surfaces 
of  every  sort  and  all  built  in  good  order,  and  where  it  can  be 
cleaned  and  pipes  constantly  full. 

n  =  .013:  unplaned  timber  when  all  joints  are  good,  such  as 
should  be  the  case  in  all  penstocks,  full  of  water  at  all  times. 

n  =  .0135:  ashlar  masonry  and  well-laid  brickwork,  riveted 
steel  pipes,  common  cast-iron  pipes  after  a  year's  use,  earthen 
and  stoneware  pipe  in  good  condition  but  not  new;  plaster, 
and  planed  wood  in  bad  condition,  and  generally  the  materials 
mentioned  with  n  =  .012  when  same  is  inaccessible  and  high 
velocities. 

n  =  .015:  second  class  or  rough  faced  brickwork,  well  dressed 
stonework,  foul  and  slightly  tuberculated  iron,  cement  and  terra 
cotta  pipes  with  bad  joints,  and  old;  high  velocities. 


MEASUREMENT  OF  FLOW.  23 

n  =  .017:  brickwork,  ashlar  and  stoneware  in  bad  condition, 
tuberculated  iron  pipes,  rubble  in  cement  or  plaster  in  good 
order,  fine  gravel  well  rammed,  of  one-third  to  two-thirds 
inches  diameter;  and  generally  the  materials  mentioned  for 
n  =  .013  when  same  are  in  bad  order,  and  low  velocities  used. 

n  =  .02:  rubble  in  cement  in  bad  condition,  coarse  rubble, 
rough  set  and  undressed;  coarse  rubble  set  dry;  disintegrated 
brickwork  and  masonry;  coarse  gravel  well  rammed  from  ltol$ 
inches  in  diameter;  canals  with  beds  and  banks  of  very  firm 
regular  gravel  carefully  trimmed  and  rammed,  rough  rubble 
with  bed  partly  covered  with  silt  and  mud,  penstocks  made  of 
rough  narrow  lumber  and  with  battens  over  cracks,  trimmed 
earth  canals. 

n  =  .0225:  canals  in  earth  in  first-class  condition. 

n  =  .025:  canals  and  rivers  in  earth  of  fairly  uniform  cross- 
section,  slope  and  direction  in  good  shape  and  free  from  loose 
stones  and  weeds. 

n  =  .0275:  canals  and  rivers  below  the  average  in  order  and 
regimen. 

n  =  .03:  canals  and  rivers  in  earth  in  rather  bad  order  and 
regimen,  having  loose  stones  and  occasional  weeds  and  detritus 

n  =  035:  rivers  and  canals  with  earthen  beds  in  bad  order 
and  regimen  and  having  many  boulders,  snags,  weeds,  bends, 
ice,  etc. 

n  =  .055:  torrential  streams  of  high  velocity  filled  with 
boulders,  etc. 

U.  S.  engineers  found  that  for  the  Susquehanna  River  dur- 
ing the  great  flood  of  1904  when  the  river  was  out  of  its  banks 
and  running  through  timbered  land,  over  islands,  etc.,  that 
n  =  .055. 

CIRCULAR  PENSTOCKS. 

We  now  have  the  data  necessary  to  find  the  quantity,  Q. 
The  first  step  is  to  select  the  coefficient  n,  and  from  Table  IV 
find  the  corresponding  value  of  A  C  \/~r  for  the  particular  pipe 
under  consideration.  Then  from  Table  V  the  value  of  \/s  is 
found  which  corresponds  to  the  pipe  and  fall  per  mile  under 
consideration.  These  values  substituted  in  the  formula  Q  =  \/s 

C  \/7  give  us  the  flow  in  cubic  feet  per  second. 
*The  above  values  have  been  made  to  a^ree  with  latest  experiments. 


24 


HYDROELECTRIC  PLANTS 


TABLE  IV.  (Kent) 
FOR  CIRCULAR  PIPES  FLOWING  FULL.     VALUES  OF  A  C  vT  IN  KUTTER'S  FORMULA. 


Diam. 
ft.  in. 

VALUE  OF  AC\/^ 

n  =  .010 

n  =  .011 

n  =  .012 

n  =  .013 

n  =  .015 

n  =  .017 

6 

6.906 

6.0627 

5.3800 

4.8216 

3.9640 

3.329 

9 

21.25 

18.742 

16.708 

15.029 

12.421 

10.50 

1  0 

46.93 

41.487 

37.149 

33.497 

27.803 

23.60 

1  3 

86.05 

76.347 

68.44 

61.867 

51.600 

43.93 

1  6 

141.2 

125.60 

112.79 

102.14 

85.496 

72.99 

1  9 

214.1 

190.79 

17  .66 

155.68 

130.58 

111.8 

2 

307.6 

274.50 

247.33 

224.63 

188.77 

164. 

2  3 

421.9 

377.07 

340.10 

309  .  23 

260.47 

223.9 

2  6 

559.6 

500.78 

452.07 

411.27 

347.28 

299.3 

2  9 

722.4 

647  .  18 

584.90 

532.76 

451.23 

388.8 

3 

911.8 

817.50 

739.59 

674.09 

570.90 

493.3 

3  3 

1128.9 

1013.1 

917.41 

836.69 

709.56 

613.9 

3  6 

1374.7 

1234.4 

1118.6 

1021.1 

866.91 

750.8 

3  9 

1652.1 

1484.2 

1345.9 

1229.7 

1045. 

906. 

4 

1962.8 

1764.3 

1600.9 

1463.9 

1245.3 

1080.7 

4  6 

2682.1 

2413.3 

2193. 

2007. 

1711.4 

1487.3 

5 

3543. 

3191.8 

2903.6 

2659. 

2272.7 

1977. 

5  6 

4557.8 

4111.9 

3742.7 

3429. 

2934.8 

2557  .  2 

6 

5731.5 

5176.3 

4713.9 

4322. 

3702.3 

3232.5 

6  6 

7075  .  2 

6394.9 

5825.9 

5339. 

4588.3 

4010. 

7 

8595  .  1 

7774.3 

7087. 

6510. 

5591.6 

4893. 

7  6 

1029G. 

9318.3 

8501  .8 

7814. 

6717. 

5884.2 

8 

12190. 

11044. 

10083  . 

9272. 

7978.3 

6995.3 

8  6 

14298. 

12954. 

11832. 

10889  . 

9377.9 

8226.3 

9 

16604. 

15049. 

13751  . 

12663. 

10917. 

9580  .  7 

9  6 

19118. 

17338. 

15847  . 

14597  . 

12594. 

11061. 

10 

21858. 

39834. 

18134. 

16709. 

14426. 

12678  . 

10  6 

24823  . 

22534. 

20612. 

18996  . 

16412. 

14434. 

11 

28020  . 

25444. 

23285  . 

21464. 

18555  . 

16333  . 

11  ff 

31482. 

28593  . 

26179. 

24139. 

20879  . 

18395. 

12 

35156. 

31937. 

29254  . 

26981  . 

23352. 

20584  . 

12  6 

39104. 

35529  . 

32558  . 

30041. 

26012. 

22938  . 

13 

43307  . 

39358  . 

36077  . 

33301  . 

28850  . 

25451  . 

13  6 

47751  . 

43412. 

39802  . 

36752  . 

31860. 

28117. 

14 

52491  . 

47739  . 

43773  . 

40432  . 

35073  . 

30965. 

14  6 

57496  . 

52308  . 

47969  . 

44322  . 

38454. 

33975  . 

15 

62748  . 

57103. 

52382  . 

48413. 

42040  . 

37147  . 

16 

74191  . 

67557  . 

62008  . 

57343  . 

49823  . 

44073  . 

17 

86769  . 

79050  . 

72594  . 

67140. 

58387  . 

51669. 

18 

100617  . 

91711. 

84247  . 

77932  . 

67839  . 

60067  . 

19 

115769. 

105570. 

96991  . 

89759  . 

78201  . 

69301  . 

20 

132133. 

120570. 

110905. 

102559. 

89423  . 

79259  . 

EXAMPLE  :  It  is  desired  to  carry  60,000  cubic  feet  of  water 
per  minute  a  distance  of  six  miles  with  a  loss  of  head  of  6  feet. 
A  wooden  stave  pipe  built  of  planed  staves  is  to  be  used. 

Under  these  conditions  we  should  select  n  as  =  to  .01.  From 
Table  IV  we  find  that  for  n  =  .01  and  for  a  pipe  14  feet  in 


MEASUREMENT  OF  FLOW, 


25 


diameter  (trial  size),  A  C  V>  =  52,491  and  from  Table  V  we 
find  that  for  a  fall  of  one  foot  per  mile  V^  =  .013762.  There- 
fore Q  =  .013762X52,491  =  722.38  cubic  feet  per  second,  or 
43,342  cubic  feet  per  minute.  This  is  not  a  large  enough  flow, 
so  we  next  try  a  16  foot  pipe  for  which  A  C  \/r  =  74,191  and 
-x/5  =  -013762  and  A  C  \/7  \/^  =  61,260  cubic  feet  per  minute. 
Knowing  the  size  of  pipe  and  the  quantity  of  water  flowing 


C7/ 


f 


O./  O.£          O.3          O.-4          O.-5         O.ff        0.7"          O.3         O.9  /O  //  /-? 

ft~oporfron  or^frea,  D/schsfrige  or  Ife/oc/fy 

FIG.  31. 

the  velocity  is  obtained  by  dividing  the  quantity  Q,  by  the 
area  of  the  pipe  in  square  feet. 

The  velocity  may  also  be  obtained  from  the  curves,  Fig.  31, 
and  it  is  a  good  policy  to  use  both  methods  as  a  check  on  the 
calculations. 

Table  V  will  be  found  useful  in  getting  the  square  roots  of 
the  various  values  of  s. 

FLOW  IN  PENSTOCKS. 
We    have    Kutter's    formula,    v  =  C  \/7T    where 


HYDROELECTRIC  PLANTS. 


0° 


S3 


0-0 


radius  (rj 

O.S          ~06  0.7          08 


O.f  O3  0-4 


03  JL 


FIG.  32, 


MEASUREMENT  OF  FLOW. 


27 


C  = 


n 


.5521  +     23 


[ 


This  is  a  rather  laborious  equation  and  in  Fig.  32  is  given  a 
set  of  curves  from  which  C  may  be  easily  found.  Each  curve 
is  for  a  certain  value  of  n  as  given  on  page  22  and  a  corresponding 
hydraulic  mean  radius,  r. 


These  curves  give  very  close  results  for  all  slopes  greater 
than  5  =  .0005  or  3  feet  per  mile,  and  pipes  of  greater  diameter 
than  10  inches.  For  smaller  slopes  or  penstocks  the  curves 
give  fairly  approximate  values. 

EXAMPLE. — 20,000  cubic  feet  of  water  per  minute  is  to  be 
carried  one  mile  with  a  fall  of  5  feet.  What  is  the  proper  size 


FIG.  34. 


FIG.  35. 


for  the  penstock  if  built  of  planed  lumber  and  well  constructed? 

For  a  trial  size  assume  a  section  as  shown  in  Fig.  33,  5  = 
.000947,  n=  .01,  r  =  (6x6)^(6  +  6  +  6)  =  2. 

Now  from  curve  for  n  =  .01,  Fig.  32,  and  r  =  2,  we  find  that 
C  =  172.  Substituting  these  values  in  v  =  C  \/r  s  we  have 
v  =  172  V2X. 000947  =  7.5026  feet  per  second,  or  450  feet  per 


28 


HYDROELECTRIC  PLANTS. 


minute.  As  the  area  of  the  penstock  =  36  square  feet,  cubic 
feet  per  minute  =  450X36  =  16,200  which  is  not  large  enough, 
so  we  take  a  section,  say,  7X7  =  feet. 

Then   r  =  2.33   and   C  =  175.     175X%/r7=  v  =  175X.047, 

TABLE  V.   (Kent). 
FALL  IN  FEET  PER  MILE,  SLOPE,  SINE  OF  SLOPE  AND  SQUAPE  ROOT  OF  THE  SINE. 


Fall  in  ft. 
per  mile. 

Slope 
1  ft.  in- 

Sine  of  angle 
of  slope 

Fall  in  ft. 
per  mile. 

Slope 
1  ft.  in- 

Sine  of  angle 
of  slope. 

H 

H 

L 

Vs 

H 

L 

5 

v7 

0.25 
.30 

21120. 
17600  . 

.0000473 
.0000568 

.003881 
.007538 

17. 
18. 

gto.a 

293.3 

.0032197 
.0034091 

.056742 
.058388 

.40 

13200  . 

.0000758 

.008704 

19. 

277.9 

.0035985 

.059988 

.50 

10560  . 

.0000947 

.009731 

20. 

264. 

.0037879 

.061546 

.60 

8800. 

.0001136 

.010660 

22 

240. 

.0041667 

.064549 

.702 

7520. 

.0001330 

.011532 

24. 

220. 

.0045455 

.067419 

.805 

6560. 

.0001524 

.012347 

26. 

203.1 

.0049242 

.070173 

.904 

5840  . 

.0001712 

.013085 

28. 

188.6 

.0053030 

.072822 

1. 

5280. 

.0001894 

.013762 

30. 

176. 

.0056818 

.075378 

1.25 

4224. 

.0002367 

.015386 

35.20 

150. 

.0066667 

.081650 

1.5 

3520. 

.0002841 

.016854 

40. 

132. 

.0075758 

.087039 

1.75 

3017. 

.0003314 

.018205 

44. 

120. 

.0083333 

.091287 

2. 

2640. 

.0003788 

.019463 

48. 

110. 

.0090909 

.095346 

2.25 

2347. 

.0004261 

.020641 

52.8 

100. 

.010 

.1 

2.5 

2112. 

.0004735 

.021760 

60. 

88. 

.0113636 

.1066 

2.75 

1920. 

.0005208 

.022822 

66. 

80. 

.0125 

.111803 

3. 

1760. 

.0005682 

.023837 

70.4 

75. 

.0133333 

.115470 

3.25 

1625. 

.0006154 

.024807 

80. 

66. 

.0151515 

.  123091 

3.5 

1508. 

.0006631 

.025751 

88. 

60. 

.0166667 

.1291 

3.75 

1408. 

.0007102 

.026650 

96. 

55. 

.0181818 

.134839 

4. 

1320. 

.0007576 

.027524 

105.6 

50. 

.02 

.141241 

5. 

1056. 

.0009470 

.030773 

120. 

44. 

.0227273 

.150756 

6. 

880. 

.0011364 

.03371 

132. 

40. 

.025 

.158  14 

7. 

754.3 

.0013257 

.036416 

160. 

33. 

.0303030 

.174077 

8. 

660. 

.0015152 

.038925 

220. 

24. 

.0416667 

.204124 

9. 

586.6 

.0017044 

.041286 

264. 

20. 

.05 

.223607 

10. 

528. 

.0018939 

.043519 

330. 

16. 

.0625 

.25 

11. 

443.6 

.0020833 

.045643 

440. 

12. 

.0833333 

.288675 

12. 

440. 

.0022727 

.047673 

528. 

10. 

.1 

.316228 

13. 

406.1 

.0024621 

.04962 

660.0 

8. 

.125 

.353553 

14. 

377.1 

.0026515 

.051493 

880. 

6. 

.1666667 

.408248 

15. 

352. 

.0028409 

.0533 

1056. 

5  . 

.2 

.447214 

16. 

330  . 

.0030303 

.055048 

1320. 

4. 

.25 

.5 

which  gives  a  velocity  of  8.225  feet  per  second,  and  a  flow  of 
24,180  cubic  feet  per  minute,  which  is  too  much.  Another 
trial  gives  a  section  of  6  feet  4  inches  X  7  feet  as  having  a  capacity 
of  21,360  cubic  feet  per  minute,  which  is  about  right. 


MEASUREMENT  OF  FLOW. 


29 


SHORT  PIPES. 

The  flow  through  such  pipes  is  affected  by  three  quantities; 
frictional  resistance  such  as  has  been  already  considered,  losses 
due  to  setting  quiet  water  into  motion  and  a  loss  due  to  the 
shape  of  the  orifice. 

TABLE  VI  (Kent). 

Values  of  \/~^  for  circular  pipes,  sewers,  and  penstocks  of  different  diameters,     r  =  mean 
area 


hydraulic  depth  = 


full. 


perimeter 


diameter  for  circular  pipes  running  full  or  exactly  half 


Diam. 
ft.          in.  « 

/-  in  ft. 

Diam. 
ft.       in. 

\/r   in  ft. 

Diam. 
ft.           in. 

Vr    in  ft- 

Diam 

ft. 

in. 

Vr   in  ft- 

i 

.088 

2 

.707 

4 

6 

1.061 

9 

1.500 

i 

.102 

2 

1 

.722 

4 

7 

1.070 

9 

3 

1.521 

l 

.125 

2 

2 

.736 

4 

8 

1.080 

9 

6 

1.541 

i 

.144 

2 

3 

.750 

4 

9 

1.089 

9 

9 

1.561 

11 

.161 

2 

4 

.764 

4 

10 

1.099 

10 

1.581 

H 

.177 

2 

5 

.777 

4 

11 

1.109 

10 

3 

.601 

if 

.191 

2 

6 

.790 

5 

1.118 

10 

6 

.620 

2 

.204 

2 

7 

.804 

5 

1 

1.127 

10 

9 

.639 

2* 

.228 

2 

8 

.817 

5 

2 

1.137 

11 

.658 

3 

.251 

2 

9 

.829 

5 

3 

1.146 

11 

3 

.677 

4 

.290 

2 

10 

.842 

5 

4 

.155 

11 

6 

.696 

5 

.323 

2 

11 

.854 

5 

5 

.164 

11 

9 

.714 

6 

.354 

3 

.866 

5 

6 

.173 

12 

.732 

7 

.382 

3 

1 

.878 

5 

7 

.181 

12 

3 

.750 

8 

.408 

3 

2 

.890 

5 

8 

.190 

12 

6 

.768 

9 

.433 

3 

3 

.901 

5 

9 

.199 

12 

9 

.785 

10 

.456 

3 

4 

.913 

5 

10 

.208 

13 

.083 

11 

.479 

3 

5 

.924 

5 

11 

.216 

13 

3 

.820 

.500 

3 

6 

.935 

6 

.225 

13 

6 

.837 

1 

.520 

3 

7 

.946 

6 

3 

.250 

14 

.871 

2 

.540 

3 

8 

.957 

6 

6 

1.275 

14 

6 

.904 

3 

.559 

3 

9 

.968 

6 

9 

1.299 

15 

• 

.936 

4 

.577 

3 

10 

.979 

7 

1.323 

15 

6 

.968 

5 

.595 

3 

11 

.990 

7 

3 

1.346 

16 

2. 

6 

.612 

7 

6 

1.369 

16 

6 

2.031 

1           7 

.629 

1 

.010 

7 

9 

1.392 

17 

2.061 

1          8 

.646 

2 

.021 

8 

1  .414 

17 

6 

2.091 

1           9 

.661 

3 

.031 

8 

3 

1.436 

18 

2.121 

1        10 

.677 

4 

.041 

8 

6 

1.458 

19 

2.180 

1        11 

.692 

5 

.051 

8 

9 

1  .479 

20 

2.236 

To  find  the  diameter  D  of  a  short  pipe  of  length  L,  which  is 
to  carry  a  given  quantity  Q  of  water  per  minute  under  a  head 
H,  substitute  values  for  D  in  the  formula 


(37.6  D+L) 


until  the  equation  is  satisfied. 


30 


HYDROELECTRIC  PLANTS. 


If  the  orifice  is  given  a  slant  as  per  dotted  line  (Fig.  34)  the 
flow  will  be  materially  reduced. 

The  inlet  on  short  penstocks  where  the  entrance  loss  would 
be  an  important  portion  of  the  whole  lost  head,  should  be  pro- 
vided with  a  conical  entrance  piece  as  in  Fig.  35;  to  avoid  a 
large  gate,  the  cone  may  project  out  into  the  head  water  as 
shown. 

FLOW  OF  AIR  IN  PIPES. 

Air  flows  in  a  pipe  under  the  same  laws  as  water  in  a  penstock, 
the  only  difference  being  in  the  coefficient  of  friction. 

v2L 
H  =  10,000  D5  d 

wherein  D  is  the  diameter  of  the  pipe  in  inches,  L  the  length  of 
the  pipe  in  feet,  V  the  volume  of  air  delivered  in  cubic  feet  per 
minute,  H  the  pressure  lost  in  transmission,  and  d  a  constant. 

A  hydro-compressor  delivers  the  air  to  the  pipe  line  at  the 
temperature  of  the  water  and,  therefore,  does  not  require 
cooling.  In  other  words,  the  pressure  will  not  drop  off  due 
to  cooling  while  being  transmitted  through  the  pipes. 

TABLE  VII. 
LIMITING  VELOCITIES  FOR  AIR. 

Diameter  of  pipe  in  feet 4       6       8     10     12 

Velocity  in  feet  per  second... 18     12     11      10       9       8 

The  above  velocities  are  extreme  and  should  be  avoided. 

TABLE  VIII   (F.   Richard). 
a  FOR  WROUGHT  IRON  PIPE. 


Diameter  Pipe 
in  inches. 

« 

Diameter  Pipe 
in  inches. 

a 

1 

.35 

5 

0.934 

H 

.50 

6 

1.00 

H 

.662 

8 

1  .125 

2 

.665 

10 

1.2 

2* 

.65 

12 

1.26 

3 

.73 

16 

1.34 

3} 

.787 

20 

1.40 

4 

.84 

24 

1.45 

MEASUREMENT  OF  FLOW. 


31 


TABLE  IX  (F.  Richard). 
POWER  OBTAINABLE  FROM  ONE  POUND  OF  COMPRESSED  AIR  USED  WITHOUT  HEATING 


Pressure  Ibs.  per  sq.  in. 

H.p.  per 
cubic  ft. 
of  air 
per  sec. 

Of 

Compression. 

Alter  cooling 
to  60°  F. 

100 

57.34 

56.6 

95 

55.30 

55.4 

90 

53.17 

54.0 

85 

51.11 

52.7 

80 

48.96 

51.2 

75 

46.59 

49.2 

70 

44.53 

47.7 

65 

42.24 

45.8 

60 

39.92 

43.7 

55 

37.52 

41.4 

50 

35.06 

38.7 

45 

32.58 

35.8 

40 

29.94 

32.4 

35 

27.21 

28.4 

30 

24.39 

23.7 

CANALS. 

The  calculations  for  the  flow  in  canals  are  even  more  com- 
plicated than  for  penstocks  on  account  of  the  greater  variation 
of  n.  This  coefficient  varies  for  each  particular  soil  and  lining 
and  may  equal  .012  for  one  section  and  .035  for  the  next.  In 
selecting  the  value  for  n  always  take  a  value  .01  larger  than 
called  for  in  the  list  given  on  page  22.  The  form  of  cross- 
section  depends  principally  on  the  soil  through  which  the  canal 
is  cut.  The  velocity  is  selected  so  that  the  linings  will  not 
be  disturbed  by  the  flowing  water  and  sufficient  velocity  given 
to  the  flow  so  that  silt  will  not  be  deposited. 

The  banks  of  the  canal  must  be  made  so  flat  that  when  they 
are  wet  they  will  not  run  down  into  the  canal  or  change  their 
form  in  any  way. 

Grass  will  form  in  most  canals,  but  this  can  be  mowed  out 
and  need  not  be  considered. 


32 


HYDROELECTRIC  PLANTS. 


TABLE  X. 
SAFE  VELOCITIES  FOR  CANALS,  AT  WHICH  THE  VARIOUS  SOILS 

WILL  NOT  WASH. 
Soft  brown  earth  .........  Safe  mean  velocity  ft.  per  sec. 

Soft  loam  ........  .  ......         "  "  "       " 

Sand  ................... 

Gravel  ..................          " 

Pebbles  (most  gravel)  ____ 

Broken  stones,  flint  ......  "  "       " 

Conglomerate,  soft  slate.  .  "      .  " 

Pure  clay  ...............          " 

Stratified  rock  ...........  "       " 


Hard  rock  ............  ...  "  " 

These  values  are  recommended  by  Kutter  as  being  safe. 


0.328 
.656 
1.312 
2.625 
3.938 
5.579 
6.564 
7.000 
8.204 
13.127 


'  EFFECT  OF  ICE  ON  THE  FLOW. 

In  all  northern  latitudes,  due  allowance  must  be  made  for 
the  ice  forming  in  the  canal,  which  not  only  reduces  the  area 


FIG.  36. 

but  also  increases  the  wetted  perimeter.  The  coefficient  n 
for  the  surface  of  the  ice  may  be  assumed  to  be  equal  to  that 
for  a  canal  in  earth  or  .024. 

EXAMPLE.  —  Find  the  difference  between  the  capacities  of  the 
canal  shown  in  Fig.  36  having  a  fall  of  one  foot  to  the  mile 
when  free  from  ice,  and  when  frozen  over  as  shown.  (1)  Canal 

1200 

free  from  ice:  The  area,  A,  =  1200  square   feet,   r  = 

n  -  .024. 


n 


From  Kutter  's  formula 


MEASUREMENT  OF  FLOW. 


33 


Substituting 


23  + 


I 


.00155 


.024     .000189 


.024 


XV  9.68  X.  000189 


IV9.68 

91. 7X. 0428  =  3.92  feet  per  second,  and  Q  =  1200X3.92  =  4700 

cubic  feet  per  second. 

(2)  Canal  frozen  over  with  ice  24  inches  thick. 

1000 


A  =  1000.     r  = 


220 


=  4.545,  n 


.024 


Solving  for  v,  v  =  2.31  and  Q  =  1000X2.31  =  2310. 

Thus  it  will  be  seen  that  the  ice  causes  a  loss  in  the  efficiency 
of  the  canal  of  about  49  per  cent.  In  the  case  of  a  shallow, 
broad  canal  with  rough  bottom,  the  loss  is  proportionately 
greater. 


0        S 


FIG.  37. 


Therefore,  in  selecting  the  size  of  section  do  not  fail  to  allow 
for  ice. 

RIVERS,  PRELIMINARY  MEASUREMENTS. 

As  most  frequently  happens  the  stream  to  be  measured  13 
.too  wide  and  deep  to  warrant  the  construction  of  a  weir,  in 
which  case  some  other  method  must  be  adopted. 

Select  some  place  along  the  river  where  for  from  50  to  100 
feet  the  water  is  of  uniform  depth  and  width,  and  measure  off 
along  the  banks  a  certain  distance,  say  100  feet,  as  in  Fig.  37. 
Divide  this  distance  into  10-foot  lengths,  and  mark  the  divi- 
sions with  stakes.  Take  a  dry  piece  of  wood  and  wreight  one 
end  so  that  when  thrown  into  the  water  it  will  stand  almost 
upright,  and,  as  it  floats,  just  clear  the  bottom  of  the  stream. 
A  piece  of  lead  pipe  is  a  handy  thing  for  this  purpose  as  it  may 
be  cut  to  any  length,  and  easily  nailed  to  the  float. 


34  HYDROELECTRIC  PLANTS. 

Have  an  assistant  on  the  bank  with  a  watch  and  note  book. 
Throw  the  float  into  the  stream  above  the  first  stake  and  when 
it  has  floated  down  even  with  it,  the  assistant  takes  the  time. 
Then  run  down  and  stand  ready  to  catch  the  float  when  it 
•gets  even  with  the  last  stake,  and  as  it  arrives  at  that  point 
call  out  and  the  assistant  catches  the  time.  The  number  of 
seconds  it  has  taken  the  float  to  move  100  feet  is  then  entered 
in  the  note  book.  A  large  number  of  these  readings  should  be 
taken,  and  the  float  thrown  in  at  different  places  across  the 
stream  so  as  to  get  the  average  velocity  of  the  water.  All 
these  measurements  added  up  and  divided  by  their  number, 
now  gives  the  average  time  it  takes  the  float  to  move  100  feet. 
The  average  velocity  of  the  river  will  be  from  85  to  95  per  cent, 
of  this,  depending  on  the  unevenness  of  the  river  bed. 

Now  take  a  rod  divided  into  feet  and  inches,  and,  starting 
across  the  stream  even  with  the  first  stake,  measure  the  depth 


FIG.  38. 

every  three  or  four  feet,  as  at  1,  2,  3,  4,  etc.,  being  careful  to 
set  the  rod  on  top  of  the  inequalities  rather  than  down  in  be- 
tween them.  Repeat  this  operation  across  from  every  one  of 
the  ten  stakes  and  then  add  up  all  the  soundings  and  divide  the 
sum  by  the  number  of  the  readings  taken.  This  gives  the  aver- 
age depth  in  feet.  Next  get  the  width  of  the  stream  opposite 
each  stake,  as  A  A ',  B  Bf,  etc.,  and  divide  by  the  number  of 
measurements,  getting  the  average  width. 

Now  to  get  the  cubic  feet  of  water  flowing  per  minute  mul- 
tiply the  average  width  by  the  average  depth  and  this  product 
by  the  velocity  of  the  water  in  feet  per  minute. 

A  cubic  foot  of  water  weighs  slightly  more  than  62J  pounds. 
Therefore  the  number  of  cubic  feet  of  water  found  to  be  flowing 
each  minute  multiplied  by  62 J  (62J  is  generally  used) ,  gives  the 
pounds  of  water  flowing  each  minute. 

The  writer  has  found  that  in  this  way  remarkably  close  re- 


MEASUREMENT  OF  FLOW. 


35 


suits  can  be  obtained,   not   varying  more  than  five  per  emit, 
from  measurements  made  with  a  standard  weir. 

One  of  the  most  reliable  floats  consists  of  a  jointed  tube 
closed  at  one  end.  Fig.  38.  The  joints  are  short  enough  to 
easily  pack  away  and  about  2  inches  in  diameter.  In  making 
the  measurements  enough  joints  are  screwed  together  so  that 
when  sufficient  shot  is  put  in  to  sink  the  bottom  to  within 
a  few  inches  of  the  river  bed,  the  top  is  just  out  of  water.  Cur- 
rent meters  are  often  used  for  measuring  the  velocity  of  a 
stream. 

CURRENT  METERS. 

Fig.  39  shows  the  two  types  of  current  meters  which  are 
commonly  used.  The  one  at  the  right,  is  of  the  cup  vane 


FIG.  39. — Revolving  type  current-meter. 

type,  and  the  one  at  the  left  of  the  helical.  In  each  case  the 
meter  is  mounted  on  a  long  pole  or  rod  and  lowered  into  the 
water.  The  current  causes  the  vanes  to  revolve  and  the  in- 
strument is  so  calibrated  that  a  certain  number  of  revolutions 
of  the  vanes  indicates  a  certain  velocity  of  the  water.  By 
proper  gearing  one  of  the  gears  is  made  to  revolve  once  for 
each  passing  foot  of  water.  The  revolution  of  this  gear  is 
made  known  to  the  observer  either  by  electrically  ringing  a 
bell  or  by  causing  a  click  which  may  be  heard  along  the  rod. 
It  will  be  seen  that  these  instruments  depend  for  their  accu- 
racy upon  the  constancy  of  the  coefficient  of  friction  of  the 


36 


HYDROELECTRIC  PLANTS. 


numerous  bearings.  These  bearings  are  in  agate  mostly  and 
yet  a  small  piece  of  river  grass  or  a  grain  cf  sand  can  cause  a 
great  inaccuracy  in  the  reading.  On  this  account  they  mvst 
be  frequently  inspected,  cleaned  and  re-calibrated. 

It  was  to  avoid,  as  much  as  possible,  these  sources  of  error, 
that  the  author  designed  the  current  meter  shown  in  Fig.  40. 
In  this  meter  the  current  strikes  the  vane,  causing  it  to  rotate 
on  the  pivot  g ;  attached  to  the  pivot  is  a  light  i-inch  brass  tube 
a  having  at  its  upper  end  a  pointer  c.  Being  rigidly  connected 


FIG.  40. — Direct  reading  type  current-meter. 

to  the  vane  the  pointer  c  indicates  the  exact  position  of  the  vane  /. 
Now  to  bring  the  vane  back  when  acted  on  by  the  flow  to  its 
position  at  right  angles  to  the  current  and  the  pointer  c  to  0, 
the  thumb  screw,  h,  is  turned.  This  thumb  screw  is  attached 
to  the  torsion  wire  d  and  the  wire  is  attached  to  the  pivot  g. 
Therefore  by  turning  the  screw  h  the  vane  is  moved  back  and 
the  pointer  k  attached  to  the  thumb  screw,  to  some  position, 
say  175.  The  torsion  in  the  wire  is  directly  proportional  to 
the  pressure  on  the  vane,  or  the  velocity  of  the  water,  so  the 
reading  will  be  175  feet  per  minute.  On  the  dial  the  scale,  made 


MEASUREMENT  OF  FLOW  37. 

from  actual  tests,  is  placed,  and  gives  the  velocity  in  feet  per 
minute  (see  plan  view).  When  a  velocity  is  wanted  all  that  is 
necessary  is  to  stick  the  meter  in  tne  water  with  the  va.ne  about 
perpendicular  to  the  current  and  then  rotate  the  thumb  screw 
till  C  comes  to  0.  By  taking  the  highest  reading  of  the  pointer 
k,  C  being  kept  at  0,  it  will  be  known  that  the  vane  is  per- 
pendicular to  the  current. 

In  tnis  instrument  there  is  no  rotation  of  delicate  parts, 
the  vane  only  moving  through  an  arc  of  some  30°.  Therefore 
grit  and  grass  have  little  effect  on  it.  Depending  on  the  torsion 
of  a  steel  wire  for  its  accuracy  it  is  at  all  times  ready  for  use 
and  readings  can  be  made  as  easily  as  time  can  be  taken 
from  a  watch.  The  vanes  are  detachable  and  a  set  of  four  goes 
with  each  instrument  so  that  the  greatest  sensitiveness  of  the 
instrument  may  be  used  for  all  currents.  Thus  for  a  very  slow 
current  a  large  vane  is  used  and  for  a  swift  current  a  small  vane. 
When  using  any  but  the  standard  vane  the  readings  have  to 
be  multiplied  by  a  constant.  This  meter  is  made  jointed  so 
that  it  may  easily  be  carried  in  a  suit  case,  its  weight  being  but 
two  or  three  pounds. 

EXTENSIVE  MEASUREMENTS. 

If  the  measurements  are  to  be  made  on  a  stream  of  great  width 
and  to  continue  during  times  of  flood,  a  cable  way  is  suspended 
over  the  selected  spot  and  a  car  is  used.  The  cable  is  marked 
every  five  or  ten  feet  depending  on  the  roughness  of  the  river 
bottom,  and  the  measurements  made  at  these  points  every 
time. 

In  taking  accurate  measurements  it  is  well  to  take  a  mean  of 
three  general  methods.  These  methods  are  as  follows: 

Six  tenths  single  point  method;  numerous  experiments  have 
shown  that  the  average  velocity  of  the  entire  area  is  found  at 
a  depth  equal  to  six  tenths  the  whole  depth.  Therefore  in 
taking  these  measurements  the  meter  is  held  at  that  depth  under 
the  water  at  each  five  or  ten  foot  mark  on  the  cable.  The 
average  of  these  mean  values  gives  the  average  velocity  of  the 
section.  Surface  single  point  method;  here  the  meter  is  held 
but  a  foot  under  the  water  at  each  point  across  the  stream  and 
the  average  taken.  This  average  is  then  multiplied  by  .85  to 
.95  to  get  the  average  velocity  for  the  section.  .95  would  be 


38  HYDROELECTRIC  PLANTS. 

used  for  streams  having  smooth  bottoms.  The  rougher  the 
bottom,  the  lower  would  be  the  average  velocity.  In- 
tegrating method;  in  this  case  the  meter  is  lowered  slowly 
and  with  a  uniform  motion  from  the  surface  to  the  bottom  and 
back  again. 

From  the  gauging  car  measurements  of  depth  are  also  taken 
at  each  interval.  The  widths  are  not  taken  as  the  profile  made 
at  the  start  shows  the  location  of  each  interval. 


CHAPTER  III. 
RECONNOISSANCE  OF  WATER  POWER. 

Up  to  a  short  time  ago  the  common  practice  has  been  to 
purchase  a  water  power  and  install  water  wheels  as  required  by 
the  increasing  business,  without  first  obtaining  exact  knowledge 
of  the  true  value  of  the  full  power  of  the  stream.  Now,  how- 
ever, when  organized  capital  and  business  foresight  are  the 
governing  factors  in  nearly  all  power  developments,  and  each 
horse  power  obtained  is  becoming  more  and  more  valuable,  it 
behooves  us  to  know  as  nearly  as  possible  the  actual  power  to 
be  had  under  the  given  conditions.  It  is  seldom  indeed  that 
the  power  to  be  derived  from  a  stream  is  not  over-estimated. 
This  is  usually  due  to  the  anxiety  of  the  owner  to  impress  the 
engineer  with  the  fact  that  he  expects  a  certain  amount  of 
power,  and  the  willingness  of  the  engineer  to  make  his  report 
agree  with  the  owner's  wishes. 

Any  man  of  average  intelligence  should  be  able  to  make 
measurements  of  his  water  power  which  will  serve  as  a  check 
on  those  taken  by  the  engineer,  and  in  most  cases  can  be  used 
as  a  basis  for  the  preliminary  estimates. 

POWER  MEASUREMENT. 

Water  power  is  measured  by  two  quantities:  pounds  of  water 
flowing  down  the  stream  each  minute,  and  the  "  fall  "  or  "  head." 
The  amount  of  head  should  be  found  by  a  competent  surveyor, 
and  as  the  limiting  factor  is  the  cost  of  the  overflowed  lands, 
the  owner  should  accompany  the  surveyor  when  the  levels  are 
run  to  see  that  no  little  brooks  or  drainage  ditches  are  overlooked. 
Sometimes  a  very  innocent  ditch  is  a  drain  for  many  acres  of 
valuable  farm  land  and  if  you  back  it  full  of  water  you  are 
liable  to  heavy  damages.  The  surveyor  can  from  time  to  time 
set  his  level  up  so  that  the  glass  is  on  a  level  with  the  crest  line 
of  the  proposed  dam,  and  by  sweeping  around  over  the  river 

39 


40  HYDROELECTRIC  PLANTS. 

bottoms,  get  a  very  good  idea  of  the  overflow.     A  county  map 
is  a  great  aid  in  getting  the  acreage  of  the  submerged  land. 

Having  obtained  the  levels,  the  area  of  the  reservoir  as  it 
will  be  when  full  should  be  roughly  approximated,  as  its  extent 
will  be  of  use  in  determining  the  value  of  the  power. 

The  head  in  feet  being  obtained,  the  next  item  should  be 
the  pounds  of  water  flowing  in  the  stream  each  minute.  Great 
care  should  be  exercised  in  determining  this  item. 

'  To  be  safe  these  measurements  should  extend  over  several 
years  as  the  yearly  flow  varies  between  wide  limits,  but  usually 
this  is  impossible.  Measurements  taken  at  any  other  than 
during  the  time  of  low  water  will  be  untrustworthy  as  it  is 
with  the  minimum  we  usually  have  to  deal.  In  determining 
these  periods  of  low  water,  if  the  observer  is  a  stranger  in  the 
vicinity  of  the  proposed  dam,  he  may  ask  several  of  the  old 
fishermen  and  hunters,  but  should  not  depend  upon  merchants 
and  bankers  for  this  most  important  information.  On  many 
of  the  rivers  government  reports  may  be  obtained,  but  the 
author  would  advise  caution  in  their  use. 

The  methods  of  determining  the  flow  are  fully  explained  in 
Chapter  II. 

VALUE  OF  GOVERNMENT  REPORTS  TO  THE  HYDRAULIC  ENGINEER. 

Wishing  to  make  all  possible  use  of  the  various  reports  on 
rainfall,  run-off,  etc.,  annually  issued  by  the  United  States 
Government,  the  writer  made  an  extended  study  of  the  subject 
with  the  following  results: 

No  reliable  data  can  be  obtained  from  the  reports  on  preci- 
pation  which  will  aid  in  estimating  the  maximum  flood  flow. 
Nor  will  the  rainfall  data  be  of  use  in  predicting  the  day,  week 
or  month  when  these  extreme  floods  will  occur.  An  average 
can  be  taken,  but  outside  of  this  average  are  such  widely 
scattered  variables  that  for  practical  purposes  there  is  no  in- 
formation given. 

For  example,  take  the  Table  XI  and  note  that  during  August, 
1903,  the  rainfall  was  6.93  inches,  and  in  October  it  was  6.26. 
Yet  there  is  no  corresponding  increase  in  the  run-off.  Note 
that  for  March,  1904,  the  time  of  the  terrible  flood  which  cost 
many  lives  and  millions  of  money,  the  rain  was  only  3.08  inches. 
This  flood  was  caused  entirely  by  a  sudden  thaw  which  melted 


RECONNAISSANCE  OF  WATER  POWER. 


41 


TABLE  XI. 
RAINFALL  AND  RUN-OFF  DATA,  SUSQUEHANNA  RIVER.  AVERAGE  OF  NINETEEN  STATIONS. 


Month. 

19C 

Run- 
Off. 

3 

Rain- 
fall. 

190 
Run- 
Off. 

4 
Rain- 
fall. 

Month. 

19 

Run- 
Off. 

33 
Rain- 
fall. 

19 
Run- 
Off. 

04 
Rain- 
fall. 

Cu.  ft. 
per  sec. 
per  sq. 
mile. 

inches 

Cu.  ft 
per  sec. 
per  sq. 
mile. 

inches 

Cu.  ft. 
per  sec. 
per  sq. 
mile. 

inches 

Cu.  ft. 
per  sec. 
per  sq. 
mile. 

inches 

January.  .  .  . 

1.626 

2.60 

1.280 

3.46 

July  

1.331 

4.20 

0.800 

5.16 

February.  .  . 

3.552 

2.50 

1.620 

2.24 

August.   .  .  . 

1.053 

6.93 

0.519 

4.21 

March  

5.023 

4.93 

4.280 

3.08 

September  . 

1.277 

1.64 

0.413 

3.56 

April  

2.910 

2.01 

2.930 

2.79 

October  

1.822 

6.26 

0.698 

3.01 

May  

0.628 

0.85 

1.750 

3.64 

November.  . 

1.151 

2.24 

0.498 

1.17 

June  

1.115 

6.70 

1.290 

2.99 

December.  .  . 

0.737 

2.20 

0.407 

2.18 

Total  rainfall  for  year  =  25  inches  (1903),  and  18.7  inches  (1904). 


TABLE  XII. 
RUN-OFF  AND  RAINFALL  DATA  FOR  VARIOUS  RIVERS. 


Date 

Drainage 
area 
sq.  miles 

Run-orf 
cu.  ft.  per  sec. 
per  sq.  mile 

Chippewa  R  Eau  Claire  Wis 

1904 

G740 

1  362 

Flambeau  R,.  Ladysmith,  Wis  

1904 

2,120 

1.230 

Wisconsin  R  Merrill  Wis 

1904 

2,630 

1  850 

Rock  R  Rockton  111 

1904 

6,150 

*  761 

Illinois  R.,  Minooka,  111  
Youghiogheny  R.,  Friendsville,  Md  
Mahoning  R.,  Youngstown,  O  
Licking  R.,  Pleasant  Valley,  O  
New  R.,  Radford,  Va  
New  R.,  Fayette,  W.  Va  

190* 
1904 
1904 
1904 
1904 
1904 

6,480 
295 
958 
696 
2,725 
6,200 

1.953 
f2.120 
1.247 
.792 
.968 
.929 

Greenbrier  R  Alderson,  W  Va 

1903 

1  344 

1  480 

Greenbrier  R  Alderson,  W  Va 

1904 

1  344 

911 

Scioto  R.,  Columbus,  O  
Olentangy  R.,  near  Columbus,  O  
Wabash  R.,  Logansport,  Ind  
Tippecanoe  R.,  Delphi,  Ind  
White  R.  (E.  Branch),  Shoals,  Ind  
French  Broad  R.,  Oldtown,  Tenn  
leniessee  R  Knoxville,  Tenn 

1904 
1904 
1904 
1904 
1904 
1904 
1904 

1,051 
520 
3,163 
1,890 
4,900 
1,737 
8  990 

1.017 
1.103 
1.600 
off  10% 
.947 
1.050 
842 

Pigeon  R  Newport,  Tenn  

1904 

655 

070 

Nolichucky  R.,  Granville,  Tenn  
Halston  R.  (S.  Fork),  Bluff  City,  Tenn  
Watauga  R.,  Elizabethton,  Tenn  
Little  Tennessee  R.,  Judson,  N.  C  
Tuckasegee  R  Bryson,  N  C 

1904 
1904 
1904 
1904 
1904 

1,099 
828 
408 
675 
662 

.030 
.862 
.280 
.650 
470 

Hiwassee  R  Murphy,  N  C  . 

1904 

410 

290 

Hiwassee  R.,  Reliance,  Tenn  
Nottely  R.,  Ranger,  N.  C  
Susquehanna  R.,  McCall's  Ferry,  Pa  

1904 
1904 

1,180 
272 
1,370 

.200 
1.140 

Average  value.  .  .  .  

1.23 

1.357 

*  Minimum  is  62%  too  low. 
t  Maximum  is  58%  too  high. 

42 


HYDROELECTRIC  PLANTS. 


TABLE  XII.— (Continued.) 


Name  of  River. 

Date. 

Drainage 
area 
sq.  miles. 

Run-off 

cu.  ft.  per  sec. 
per  sq.  mile. 

Colorado  R.,  Yuma,  Arizona  
Gila  R.,  Yuma,  Arizona  
Virde  R.,  McDowell,  Arizona  

1903 
1903 
1903 

225,049 
6,000 

.069 
.085 
.0533 

Salt  R.,  McDowell,  Arizona  

1903 

6,260 

.041 

Salt  River,  Roosevelt,  Arizona  

1903 

5,756 

.061 

Tonto  Creek    Roosevelt   Arizona 

1903 

1,030 

038 

Grand  R    Klmwood  Springs  Colo 

1903 

5,838 

47 

Whiterocks  R     Whiterocks   Utah 

1903 

114 

1  23 

Bear  R.,  Collinston,  Utah  

1903 

6,000 

.20 

Sevier  R    Gunnison   Utah 

1903 

3,986 

027 

San  Pitch  R    Gunnison   Utah 

1903 

836 

045 

Humboldt  R    Oreana   Nev 

1903 

13,800 

.009 

Humboldt  R.,  Golconda,  Nev  

1903 

10,780 

.0158 

Humboldt  R.,  Palisade,  Nev  

1903 

5,014 

.066 

South  Fork  of  Humboldt  R.,  Elko,  Nev  

1903 

1,150 

.153 

East  Fork  of  Walker  R.,  Yerington,  Nev  
West  Fork  of  Walker  R.,  Coleville,  Cal  
Walker  R.,  Wabuska,  Cal  

1903 
1903 
1903 

1,130 
306 
2,420 

.103 
1.02 
.0704 

Carson  R.,  Empire,  Nev  

1903 

988 

.43 

East  Fork  of  Carson  R.,  Gardnerville,  Nev  
West  Fork  of  Carson  R..  Woodfords,  Cal  
Truckee  R    Tahoe  Cal 

1903 
1903 
1903 

381 
70 
519 

1.21 
1.70 
.40 

Truckee  R    Vista  Nev 

1903 

1,519 

.52 

Truckee  R     Pyramid  Lake,  Nev 

1903 

2,130 

.40 

Truckee  R    Mystic  Cal 

1903 

955 

.79 

Donner  Creek   Trucker  Cal 

1903 

30 

2.57 

Cache  Creek   Yolo,  Cal 

1903 

1,280 

.43 

Cache  Creek   Lower  Lake,  Cal 

1903 

500 

.67 

Feather  R    Oroville   Cal     . 

1903 

3,350 

2.11 

Stony  Creek   Fruto  Cal 

1903 

760 

.71 

Sacramento  R  ,  Red  Bluff  Cal 

1903 

9,295 

1.50 

Tuolumin  R  ,  Lagrange  Cal 

1903 

1,501 

1.82 

Merced  R  ,  Merced  Falls  Cal 

1903 

1,090 

1.28 

King  R.,  Sanger,  Cal 

1903 

1,742 

1.31 

Yule  R  ,  Portersville   Cal 

1903 

437 

.34 

Kern  R.,  Bakersfield,  Cal  

1903 

2,345 

.32 

Santa  Anna  R    Waumpingo   Cal 

1903 

182 

.46 

Mohave  R    Victorville   Cal 

1903 

400 

.37 

Yakima  R.,  Kiona,  Wash  
Yakima  R    Union  Gap  Wash 

1903 
1903 

5,230 
3,300 

1.12 
1.83 

Naches  R     North  Yakima   Wash                                      .    . 

1903 

1,000 

2.57 

Triton  R    North  Yakima  Wash                               

1903 

289 

3.15 

Missoula  R.,  Missoula,  Mont  
Brittmort  R    Grantsdale   Mont                      

1903 
1903 

5,960 
1,550 

.571 
1.007 

Weiser  R.,  Weiser,  Idaho  
Boise  R     Boise   Idaho                                                    .  . 

1903 
1903 

1,670 
2.450 

.80 
1  .28 

RECONNAISSANCE  OF  WATER  POWER.  43 

the  accumulated  snow,  and  such  a  thaw  may  occur  at  any  time 
of  the  winter. 

In  the  summer  we  are  no  more  sure  of  the  flood  periods. 
There  may  have  been  a  drought  and  then  a  terrible  rainfall. 
In  this  case  the  dry  soil  takes  up  so  much  of  the  precipation 
that  there  is  no  flood.  Another  year  is  damp  but  has  slight 
precipation.  A  heavy  rain  comes  and  the  soil  being  saturated, 
all  the  rain  runs  into  the  river  and  a  flood  is  the  result.  There- 
fore it  is  impossible  to  predict  the  flood  periods  from  rain  fall 
data.  For  the  same  river  the  run-off  changes  between  wicle 
limits,  for  the  same  rainfall  and  for  the  same  time  of  the  year. 
The  rainfall  at  one  station  bears  no  resemblance  to  that  at 
other  stations  on  the  same  drainage  area. 

From  the  government  reports  on  run-off  per  square  mile  of 
drainage  area,  data  can  be  obtained,  which  is  of  use  in  com- 
puting the  yearly  power  to  be  depended  upon.  If  the  reports 
have  extended  over  a  period  of  several  years,  a  table  like  table 
XI,  covering  that  period  will  give  an  annual  run-off  per  square 
mile  which  will  be  very  close  to  the  actual.  An  enterprise 
properly  handled  will  not  figure  on  the  results  of  the  poorest 
year,  but  will  base  the  investment  on  the  average  income  for 
a  long  period.  In  this  case  the  above  average  run-off  for  all 
the  years  will  furnish  a  safe  basis  for  estimating  the  power. 

As  will  be  seen  by  referring  to  Tables  XI  to  XIII,  the  run-off 
per  square  mile  of  drainage  area,  varies  somewhat  for  different 
rivers,  and  for  the  same  river  it  varies  with  the  year,  but  the 
average  results  are  not  so  erratic  as  to  preclude  their  use  as  a 
basis  for  estimates. 

It  will  be  noticed  that  the  Western  rivers  are  much  more 
erratic  than  those  of  the  Eastern  or  Middle  States,  but  even 
in  their  case,  by  using  judgment  in  considering  the  location  'of 
those  rivers  having  abnormal  run-off,  a  safe  average  value  can 
be  estimated  for  the  average  annual  run-off  per  square  mile 
of  drainage  area. 

The  maximum  flood  to  be  expected,  no  matter  when  it 
occurs,  is  a  matter  of  great  importance,  as  the  safety  of  the 
enterprise  largely  depends  upon  it. 

There  is  one  way,  and  only  one  way,  to  compute  this,  whether 
done  by  the  Government  or  the  engineer,  and  that  is  by  meas- 
urements made  on  the  spot.  Where  the  Government  gauging 


44 


HYDROELECTRIC  PLANTS. 


-IOO 
OfO 


t 

w 


c 
•So 


*o     b>     O     «9     M 


CO^"-O?0  •          ^ 

O     C»     10     eg        •     o 


S^       ^1  •       <N 


<N        CO        CO        — i<N.-(<N<Nr-i--.r^!N^HCO~'N^ 


RECONNAISSANCE  OF  WATER  POWER.  45 

station  has  been  established  ten  years  or  more,  the  maximum 
flood  reported  is  a  safe  figure.  But  when  there  has  not  been 
such  a  report  the  engineer  must  visit  the  site  and  make  the 
measurements.  The  highest  flood  is  always  a  matter  of  history 
among  the  inhabitants  living  near  the  river,  and  even  if  the  high- 
est flood  did  not  leave  marks  along  the  banks,  these  natives 
may  be  relied  upon.  A  house  was  moved  at  this  place,  a  drift 
log  was  left  at  another  place,  and  so  on. 

From  such  data  the  engineer  finds  the  slope  of  the  surface  of 
the  flood  for  a  distance  of  say  1,000  feet  each  side  of  the  site. 
A  profile  is  taken  at  lOOJoot  intervals.  From  this  data  and 
the  formula  Q  =  A  C  \/r  s,  given  in  Chapter  II,  the  quantity 
of  water  flowing  in  cubic  .feet  per  second  is  found.  C  would  be 
taken  at  say,  .05.  The  slope,  s,  has  been  comptued,  and  r,  the 
mean  hydraulic  radius. 

Where  the  engineer  has  the  opportunity  the  surest  way  to 
obtain  the  greatest  flood  to  be  expected  is  to  visit  the  site 
during  a  flood  and  find  the  slope  of  the  water's  surface.  Then 
from  the  marks  showing  the  stage  of  the  greatest  flood,  deter- 
mine the  proper  level  of  the  surface.  The  slope  will  be  ap- 
proximately the  same  for  both  floods  and  ris  found  from  the  profiles 
by  dividing  the  area  of  the  section  by  the  wet  perimeter.  A, 
the  area  of  the  average  section,  is  also  found  from  the  profiles. 

Frizell  gives  the  formula  Q  =  17.35  J  8QQ6  ,   where  Q  is  the 

\      A 

maximum  flood  that  may  ever  be  expected,  per  square  mile  of 
drainage  area,  and  A,  is  the  number  of  square  miles  of  the 
drainage  area. 

Applying  this  to  the  Susquehanna  river,  Q  =  17.35  «l.  8QQ6 

=  9.54.  27,666X9.54  =  262,933  cubic  feet  per  second.  The 
actual  flow  of  the  Susquehanna  on  March  8,  1904,  was  700,000 
cubic  feet  per  second.  It  will  be  seen  therefore  that  Mr.  Fr.zeH's 
formula  is  not  reliable  in  estimating  the  greatest  flow  to  be 
expected. 

RELATION  OF  PONDAGE  AND  RESERVOIRS  TO  THE  VALUATION  OF 

POWER. 

For  judging  a  power  it  is  of  prime  importance  to  know  the 
use  to  which  it  is  to  be  put,  i.e.,  one  should  have  a  general  idea 
of  the  load  curve. 


,46  HYDROELECTRIC  PLANTS. 

For  example,  consider  a  small  stream  having  an  available 
head  of  20  feet  and  a  flow  of  5000  cubic  feet  per  minute  and  a 
storage  area  of  200  acres.  First,  assume  that  it  is  desired  to 
drive  a  paper  mill  requiring  300  h.p.  This  stream,  however, 
can  not  produce  more  than  190  theoretical  h.p.,  and  since  a 
paper  mill  runs  24  hours,  the  power  is  too  small. 

Next  suppose  that  the  power  is  to  be  used  to  drive  a  factory, 
which  runs  but  10  hours  per  day.  One  acre  of  water  one  foot 
deep  contains  43,560  cubic  feet,  and  weighs  2,722,500  pounds; 
therefore  the  storage  capacity  is  43,560X200  =  8,712,000  cubic- 
feet.  The  flow  for  14  hours  during  which  the  plant  is-  idle 

,  5000  cubic  feet  X  14  hours  x  60  minutes 

would  fill  -  —  .    .  —  =  96.4  acres,  so  it 

43,560  cubic  feet  per  acre 

is  seen  that  200  acres  is  amply  large  for  this  installation  and  the 
total  energy  of  the  stream  can  be  utilized.  The  total  energy  is 
5000  cubic  feet  X  62.5  pounds,  20  feet,  24  hours 

33000"  =4550  h.p.  hours. 

4550 
which  will  give  -JTT—  =  455  h.p.  for  10  hours. 

Assuming  that  it  costs  $25.00  per  horse  power  year  to  produce 
the  power  from  coal,  the  water  power  is  worth  $11,550  per  year. 
In  this  case  it  is  purely  a  question  of  finance,  whether  the  stream^ 
is  to  be  utilized  or  not. 

Lastly,  suppose  that  the  power  can  be  used  to  light  several 
small  towns  near  by  and  a  city  of  30,000  inhabitants  six  miles 
away.  The  average  period  during  which  the  lamps  are  on 
covers  about  four  hours  so  that  the  reservoir  must  store  during 
20  hours  and  have  a  capacity  equal  to 

5000X20x60 

43560-         *  137'8  aCreS' 

therefore  it  is  seen  that  200  acres  will  be  amply  sufficient  to 
store  the  water  so  that  the  entire  energy  of  the  stream  can  be 

utilized  during  four  hours  and  the  power  will  be  — j—  =  1137.5 

h.p.  or  1 137.5 X. 0746  =  848.5  kw.  (theoretical).  The  total 
available  energy  is  848.5X4  =  3392  kw.-hrs.,  which  at  five  cents 
per  kw.-hr.  is  worth  $61,612.00  per  year. 

'  From  the  above  it  will  be  seen  how  important  it  is  to  fit  the 
tpower  to  the  market  or  the  market  to  the  power.  The  con- 


RECONNAISSANCE  OF  WATER  POWER.  47 

stantly  grinding  knives  of  the  paper  mill  demanded  a  strong, 
constant  flow,  the  factory  an  average  ten  hour  load  with  good 
storage  capacity.  The  third  case  shows  the  most  favorable 
condition  for  a  large  income  and  should  make  it  apparent  that 
it  is  worth  a  large  initial  investment  in  transmission  lines  to  so 
dispose  of  the  power. 

Suppose  now  there  is  no  reservoir  and  that  all  the  water  that 
comes  down  the  stream  is  being  used.  A  sudden  peak  comes 
in  the  load  and  as  a  result  the  water  is  drawn  from  below  the 
crest  of  the  dam  and,  since  the  entire  flow  of  the  stream  is  being 
used,  the  pond  will  not  fill  up  again  and  the  next  peak  will 
cause  it  to  be  drawn  still  lower,  with  the  result  that  the  plant 
is  soon  compelled  to  shut  down.  In  other  words,  if  there  is  no 
reservoir,  the  value  of  the  power.is  determined  by  the  minimum 
flow  per  minute,  while  in  the  last  two  cases  if  there  is  ample 
reservoir  the  value  of  the  power  is  more  than  doubled,  as  not 
only  can  the  "  peaks  "  be  taken  care  of,  but  power  can  be 
stored  during  the  idle  hours. 

The  amount  of  evaporation  on  the  surface  exposed  to  the 
sun  is  proportional  to  the  area  and  therefore  is  increased  when 
a  reservoir  is  formed.  The  evaporation  is  in  most  cases  a 
negligible  quantity,  though  under  certain  conditions  it  should 
be  taken  into  account. 

In  the  above  we  have  in  every  case  taken  the  theoretical 
power.  The  actual  power  delivered  to  the  customer  will  vary 
from  50  to  70  per  cent,  of  the  theoretical. 

By  referring  to  Table  LXXV,  the  value  of  a  reservoir  for  any 
head  can  be  estimated.  Referring  to  this  table,  an  acre  under  a 

27  50 

20-foot  head  will   give   -'    .*      =  6.88  h.p.   for  four  hours  and 

=  3.44  h. p.  for  eight  hours.     Knowing  the  value  of  the 

8 

land  and  the  power,  it  can  be  determined  how  much  land  to 
buy  for  reservoir  purposes.  In  planning  the  reservoir  due  al- 
lowance must  be  made  for  the  climate  at  that  particular  place. 
If  it  is  in  the  north  where  the  ice  freezes  several  feet  thick, 
the  reservoir  must  be  deep  enough  to  allow  for  the  ice.  It  should 
never  be  less  than  two  feet.  The  ice,  besides  reducing  the 
storage  capacity,  reduces  the  head  by  an  amount  equal  to  three- 
fourths  the  thickness  of  the  ice. 


48  HYDROELECTRIC  PLANTS. 

The  reservoir  may  be  drawn  down  two  feet,  in  which  case 
its  area  would  have  to  be  but  little  more  than  half  as  great. 
In  any  case,  the  amount  the  pond  is  to  be  drawn  down  should 
be  determined  at  the  start  and  the  plant  designed  accordingly. 
Of  course,  the  greater  the  head,  the  more  can  the  pond  be  drawn 
down  without  seriously  affecting  the  regulation  of  the  plant, 
but  in  no  case  should  the  water  be  drawn  down  so  low  that  it  will 
not  regain  the  level  of  the  dam's  crest  in  time  for  the  next  run. 

In  the  foregoing  we  have  only  treated  of  storing  enough 
water  to  carry  the  power  for  a  day  or  so,  but  it  frequently  hap- 
pens that  sufficient  pondage  can  be  secured  to  supply  the  de- 
ficient water  through  the  four  or  five  months  of  low  power. 

In  Fig.  41  is  given  a  set  of  curves  showing  the  horse-power 
and  flow  of  a  river  for  the  years  1899-1905,  these  measurements 
were  taken  on  a  weir  every  day  by  a  competent  man.  They 
are  interesting  in  many  ways.  Suppose  now  that  it  is  desired 
to  provide  a  large  reservoir  so  as  to  take  care  of  such  a  year 
as  that  in  1901,  when  for  160  days  the  power  averaged  only 
275  h.p.,  and  render  1000  h.p.  available  at  all  times. 

Fig.  42  shows  the  flow,  in  thousands  of  cubic  feet  per  minute, 
covering  the  same  period.  By  comparing  the  flow  curves  with 
the  power  curves  one  can  trace  the  variatons  of  head  and  its 
effect  on  the  power. 

Twenty  miles  up  the  river  there  is  a  valley  where,  by  building 
a  dam,  a  reservoir  12  miles  long  with  an  average  breadth  of 
1000  feet  and  depth  of  10  feet  can  be  created.  The  head  at 
the  power  house  is  70  feet,  therefore  this  reservoir  will  supply 
5280  ft.  X  12  mi  X  1000  ft.  X 10  ft.  X  62.5  Ibs.  X  70  ft.  = 

160  da.  X  600  min.  X33000 
for  160  ten-hour  days. 

A  gate  is  placed  in  the  reservoir  by  which  the  amount  of  water 
is  regulated.  This  gate  may  be  operated  by  electricity  from 
the  power  house.  The  pond  above  the  power  dam  is  kept  at 
all  times  just  full  to  the  crest  of  the  dam. 

This  upper  reservoir  has  nothing  to  do  with  the  head  at  the 
lower  dam  as  there  is  20  miles  between  the  two  dams,  its  only 
office  being  to  catch  the  flood  water  and  hold  it  for  the  future 
dry  season.  It  will  also  incidentally  aid  in  preventing  heavy 
floods  if  it  has  been  well  drawn  down  during  the  dry  weather 
and  before  the  spring  floods  come  on. 


RECONNAISSANCE  OF  WATER  POWER. 


49 


In  storing  water  for  long  periods  the  evaporation  must  be 
taken  into  account.  This,  of  course,  varies  between  wide 
limits,  being  greater  for  dry  warm  climates  than  for  cooler/and 
more  elevated  localities.  About  1/16  inch  per  day  is  a  safe 


JOOO 


</yf  *vg  jepr.  oof.  /Yor. 

FIG.  41. — Curves  showing  horse  power  in  river. 

figure  for  the  evaporation  during  the  12  months.  This  in  the 
above  example  would  make  an  evaporation  of  about  14  inches 
of  the  water  in  the  reservoir. 

The  value  of  such  a  reservoir  depends  on  the  price  for  which 


50 


HYDROELECTRIC  PLANTS. 


RECONNAISSANCE  OF  WATER  POWER.  51 

the  power  may  be  sold  and  the  cost  of  a  steam  plant  to  develop 
the  sarne  power,  the  annual  cost  of  operation  being  taken  into 
consideration.  In  comparing  the  value  of  the  large  reservoirs 
and  an  auxiliary  steam  or  gas  engine  plant,  it  must  be  borne 
in  mind  that  with  the  reservoir  peak  loads  can  be  taken  care 
of.  In  the  above  example  the  reservoir  is  worth  fully  1600 
steam  h.p.,  depending  on  the  size  of  the  peak. 

A  steam  plant  of  1600  h.p.  would  cost  all  erected,  about 
$80,000,  and  the  yearly  160  days  of  running,  during  low  water, 
and  cost  of  operation,  would  be  $21,000  including  interest, 
depreciation,  attendance,  coal,  etc.  The  cost  of  operation  of 
the  reservoir  would  only  be  the  interest  and  depreciation  so 
that  the  added  cost  of  operation  of  the  steam  plant  would  pay 
interest  on  a  very  large  expenditure  for  reservoirs. 

Frequently  several  smaller  reservoirs  may  be  found  giving 
in  the  aggregate  the  desired  capacity.  It  is  a  good  plan  where 
there  are  several  power  owners  along  the  river,  to  all  combine 
in  building  reservoirs  as  all  will  be  equally  benefited. 

Where  several  water  powers  are  situated  on  the  same  river 
and  all  using  the  power  for  about  the  same  purposes,  each 
plant  gets  the  use  of  all  the  reservoirs  above  it,  as  each  plant  is 
drawing  on  its  own  pond  and  all  the  rest  above,  thus  passing 
all  the  water  it  can  use  to  the  next  user  down  the  stream. 

PENSTOCK  WITH  RESERVOIR. 

The  possession  of  a  reservoir  in  connection  with  a  penstock 
can,  under  favorable  conditions,  increase  the  capacity  of  the 
penstock  two  fold  or  more.  Or,  with  a  reservoir  the  penstock 
need  have  but  half  the  capacity  that  it  would  have  to  have 
without  it. 

If  the  penstock  supplies  water  for  a  power  operating  24  hours 
per  day  the  capacity  of  the  reservoir  need  only  be  such  as  will 
take  care  of  the  peak  loads,  but  where  it  operates,  say  10  hours 
per  day  it  will  have  to  store  the  flow  through  the  penstock  for 
14  hours.  Without  this  reservoir  at  the  power  house  end,  the 
penstock  would  be  out  of  use  when  the  factory  was  shut  down. 

It  will  therefore  be  seen  that  it  is  of  the  utmost  importance 
to  provide  a  reservoir  at  the  power  house  end  where  long  ex- 
pensive penstocks  are  used  and  where  the  load  is  fluctuating 
or  of  short  duration. 


52 


HYDROELECTRIC  PLANTS. 


A  splendid  example  of  a  penstock  and  reservoir  is  that  of  the 
Mill  Creek  Power  Plant  near  Redlands,  Cal.,  and  a  short,  study 
of  this  plant  should  prove  instructive. 

Mill  Creek  is  a  tiny  mountain  creek  which  one  could  easily 
jump  across  or  wade  and  hardly  wet  the  ankles.  All  the  water 


FIG.  43. 

that  can  be  safely  relied  on  is  20  cubic  feet  per  second,  and  to 
get  even  this  small  amount  a  tunnel  200  feet  long  had  to  be  run 
under  the  bed  of  the  stream  to  collect  every  drop  of  seepage. 
Fig.  43  is  a  sketch  showing  the  system. 

The  tunnel  in  collecting  the  flow  and  seepage  from  the  creek 


RECONNAISSANCE  OF  WATER  POWER 


53 


picks  up  a  good  deal  of  sand.  This  sand  is  separated  from  the 
water  by  means  of  a  settling  tank  as  shown.  A  rectangular, 
open  timber  penstock  carries  the  water  from  the  tunnel  to  this 
settling  tank.  The  water  entering  the  tank  flows  from  com- 
partment to  compartment  over  the  partitions  and  leaves  the 
sand  to  settle  in  the  quiet  water.  There  are  seven  partitions 
all  of  which,  except  the  middle  one,  are  three  feet  below  the 
surface  of  the  water.  From  the  basin  the  20  cubic  feet  per 
second  passes  into  a  30  inch  gravity  penstock  having  a  fall 
of  one  foot  in  500.  This  pipe  is  called  a  gravity  pipe  because  it 
follows  the  hydraulic  gradient,  there  being  but  4  inches  of  pressure 
head  on  it  at  any  point.  Its  fall  is  regular,  a  perfect  grade  being 
necessary.  This  part  of  the  pipe  line  was  built  of  concrete  in 
the  proportion  of  one  of  cement  to  three  gravel  and  in  sections 
24  inches  long.  The  thickness  of  shell  is  2}  inches.  Fig.  44 
shows  how  two  sections  are  joined  together  by  means  of  the 


FIG.  44. 

concrete  ring  a.  The  sections  were  built  in  camps  along  the 
line  and  cost  $1  per  foot  to  make.  To  lay  the  pipe  including 
the  digging  of  the  trench  three  feet  deep  cost  $1  per  foot.  Con- 
ditions were  the  worst  possible  for  cheap  results. 

The  gravity  penstock  empties  into  a  reservoir  formed  by  a 
dam  across  a  ravine  and  has  a  capacity  sufficient  to  furnish  ten 
cubic  feet  per  second  for  six  hours.  As  will  be  shown  later  the 
loss  of  head  between  the  reservoir  and  the  power  house  is  about 
376  feet  leaving  an  effective  head  of  1906-376  =  1530  feet. 

The  reservoir  will  store  10x60x6x10  cubic  feet  or  216,000 
cubic  feet. 

Ten  cubic  feet  per  second  used  under  a  head  of  1530  feet  would 
give  1550  theoretical  h.p.  Can  there  be  a  stronger  argument 
for  a  reservoir  than  this?  Suppose  60  per  cent,  of  this  is  de- 
livered at  $50  per  h.p.,  the  annual  income  from  a  reservoir 
costing  perhaps  $5000  would  be  $46,500. 


54'  HYDROELECTRIC  PLANTS. 

Suppose  that  there  is  no  reservoir,  (Fig.  43)  and  that  the  pres- 
sure pipe  connects  directly  with  the  gravity  line.  Then  if  the 
pel  tons  were  all  suddenly  started,  the  water  in  the  pressure  pipe 
would  get  up  a  high  velocity  before  that  in  the  gravity  pipe  got 
started.  The  result  would  be  a  vacuum  in  the  gravity  pipe. 
Therefore  this  part  of  the  pipe  would  have  to  be  calculated  to 
withstand  a  vacuum  or  relief  valves  would  have  to  be  provided. 

The  pressure  which  will  collapse  a  steel  pipe  is  found  from 

P  =  806,000  ~ 

where   t  =  thickness   of  metal,   /  =  length   in   inches   between 
flanges  or  joints  and  d  =  the  diameter  of  pipe  in  inches. 

From  the  reservoir  to  the  power  house  the  fall  is  1906  feet, 
and  to  conduct  the  water  a  steel  pipe  is  used.  Here  the  ques- 
tion of  how  much  water  the  pipe  should  carry  comes  up.  If 
there  were  no  reservoir  the  answer  would  be  20  cubic  feet  per 
second,  but  having  a  reservoir,  a  pressure  pipe  having  a  suffi- 
cient capacity  to  take  care  of  the  peak  load  must  be  provided. 
This  of  course  depends  on  the  purpose  for  which  the  power  is 
used,  but  it  is  very  seldom  indeed  that  the  peak  does  not  ex- 
ceed twice  the  average  load.  On  this  basis  the  pipe  should1 
deliver  40  cubic  feet  per  second.  (See  Chapter  II.) 

Now  let  us  take  up  in  detail  the  design  of  this  complicated 
penstock,  and  calculate  the  head  lost  in  each  division. 

(1)  Rectangular  open  wooden  penstock _200  feet  long,  three 
feet  deep  and  four  feet  wide,     r  =  1.2.     V5  =  ?     Q  =  20  cubic 
feet  per  second. 

The  velocity  v  is  found  by  dividing  the  quantity  Q  by  the 
area  A  and=  1.666  feet  per  second,  v  =  C  \/r  X  \A-  n  =  -01- 
From  Table  I,  C  =  161.5.  Substituting  in  formula  for  v, 
1.666  =  161.5Xl.H8X\Aand<<T=  .0091.  Referring  to  table 
Vthe  slope  corresponding  to  one  foot  in  110  feet  or  say  the  fall 
in  the  200  feet  should  be  two  feet. 

(2)  30  inch  concrete  gravity  penstock  25,000  feet  long. 

Q  =  20.     n  =  .011.     Q=ACVr\/S' 

From  Table  III,  A  C  \/r  =  500.78.  Substituting,  20  =500.78 
X\/^and  \/i  =  .0399.  From  Table  V  we  find  the  correspond- 


RECONNAISSANCE  OF  WATER  POWER.  55 

ing  slope  to  be  one  foot  in  590.  The  slope  actually  adopted  at 
Mill  Creek  was  one  foot  in  500,  so  it  is  evident  that  the  co- 
efficient assumed  was  .01.  This,  in  the  opinion  of  the  writer, 
is  working  too  close  for  good  practice.  Certainly  a  concrete 
pipe  having  joints  every  two  feet  is  more  rough  than  good  planed 
plank. 

(3)  26  inch  steel  pipe  2480  feet  long,  riveted. 

From  Table  III  we  find  that  for  a  26  inch  clean  cast  iron  pipe 
A  C  \/7  =  302.90.  We  will  assume  that  a  riveted  steel  pipe 
has  the  same  rugosity.  As  above  explained  the  pipe  should, 
deliver  at  least  40  cubic  Jeet  per  j>econd.  Then  Q  =  A  C  ^/rX 
\/7,  or,  40  =  302.9 XV^  and  \/s~=  .132.  From  Table  VI  we 
find  the  slope  =  one  foot  in  55.  v  =  10.8  feet  per  second. 

(4)  24  inch  steel  riveted  pipe  2150  +  3450  feet  long. 

From_  Table  III  A  C  \/r  for  cast  iron  pipes  =  247.57.  Q  « 
A  C  \A-X\A  and  40  =  247.57  v^,  \7*  =  .00161.  From  Table 
V  the  slope  =  one  foot  in  36  feet. 

In  this  way  the  total  head  lost  between  the  reservoir  and 
power  house  is  found  to  be  about  200  feet.  Thus,  if  one  foot 
head  is  lost  for  every  36  feet  of  the  24  inch  pipe,  the  length  of 
;he  pipe  divided  by  36  gives  the  total  loss  of  155  feet.  Adding 
this  to  the  loss  in  the  26  inch  pipe  a  loss  of  nearly  200  feet  is 
obtained. 

The  gravity  pipe  line  pierced  the  mountains  in  19  places  in 
order  that  its  center  line  might  coincide  with  the  hydraulic 
gradient,  The  total  length  of  tunnels  was  7,490  feet.  This 
should  encourage  the  engineer  who  has  the  ordinary  proposition 
under  consideration. 

ICE  EVILS. 

» 

In  making  a  reconnoissance,  the  engineer  should  always  take 
into  consideration  the  probable  trouble  to  be  expected  from 
cold  weather. 

The  author  recently  (1906)  made  a  tour  of  the  great  water 
power  plants  in  the  northern  states  during  the  extremely  cold 
season,  and  made  a  special  study  of  the  ice  troubles  experienced 
in  operation.  A  resume'  of  the  conclusions  drawn  from  the 
investigation  is  given  below: 


56  HYDROELECTRIC  PLANTS. 

Narrow  channels  parallel  with  the  dams  and  head  works  were 
seldom  troubled  with  ice ;  plants  having  short  mill  ponds  ending  in 
rapids  or  long  shallow  ponds  ending  in  rapids  were  invariably 
troubled  with  anchor  ice;  in  ponds  which  were  frozen  over  to 
a  good  depth  the  anchor  ice  lost  its  form  before  it  got  to  the 
racks;  tail  races  which  were  not  protected  were  frozen  over 
and  clogged  unless  they  were  deep  enough  to  take  care  of  the 
water;  turbines  running  in  unprotected  steel  flumes  were,  in 
some  cases,  so  bothered  by  water  freezing  in  the  flumes  that 
housings  had  to  be  built  around  the  flume  and  fires  kept  burning ; 


FIG.  45. 

the  lowest  flow  in  the  winter  was  about  the  same  as  that  during 
the  low  water  period  in  summer. 

SOUNDINGS. 

Test  Holes. — The  natural  impulse  of  engineers  and  investors  is 
to  rush  into  a  job  without  preliminary  soundings  which  are 
to  tell  what  the  foundations  will  be.  Not  long  ago  the  author 
was  called  upon  to  inspect  a  site  for  a  dam  and  found  that  be- 
cause the  banks  on  either  side  of  the  river  were  stone,  the 
owners  had  jumped  at  the  conclusion  that  the  bottom  was  also 
stone.  $20,000  was  spent  in  getting  ready  to  build  a  masonry 
dam  and  then  it  was  found  that  there  was  no  rock  bottom. 
Often  the  rock  bottom  drops  perpendicularly  down  for  from 
50  to  100  feet  as  shown  in  Fig.  45.  The  continual  wearing  of 
the  valleys  fills  the  river  bed  below  the  ledge  with  sand  and 
gravel,  and  to  the  eye  presents  the  appearance  of  a  uniform 
river  bed.  Unfortunately  this  condition  is  most  likely  to  exist 


RECONNAISSANCE  OF  WATER  POWER,  57 

at  the  narrowest  part  of  the  river  and  between  cliffs,  just  where 
the  dam  would  naturally  be  wanted. 

Again  there  may  be  mud  holes  under  what  is  apparently 
solid  rock  bottom,  as  at  M,  Fig.  46,  and  there  may  be  several 
inches  of  mud  between  the  layers  of  rock. 

Another  condition  often  found  is  shown  in  Fig.  47.     A  founda- 


FIG.  46. 

tion  is  excavated  for  the  power  house  in  the  hard  blue  clay  and 
unless  soundings  are  made  it  would  not  be  suspected  that  at 
the  shore  side  the  foundations  rested  on  only  a  few  inches  of 
clay,  the  rest  being  quicksand.  In  this  case  the  power  house 
would  settle  badly  and  in  time  be  destroyed. 

These  three  cases  (there  are  many  more)  should  serve  to  urge 
the  engineer  and  investor  to  spend  some  money  on  sounding 
the  bottom. 


FIG.  47. 

Rock. — On  extremely  large  and  important  work  a  diamond 
drill  is  used  in  getting  a  sample  of  the  river  bed.  The  diamond 
drill  brings  to  the  surface  a  solid  core  of  rock,  an  examination 
of  which  tells  exactly  the  nature  of  the  bottom.  An  accurate 
measurement  must  be  made  of  the  depth  of  the  diamond  below 
the  surface  so  that  if  there  are  seams  in  the  rock  their  thickness 
may  be  determined. 

Soft  Bottoms. — The  common  way  of  sounding  soft  bottoms  is 
to  drive  a  gas  pipe  of  from  2J  to  4  inches  diameter  in  the  same 


58  HYDROELECTRIC  PLANTS. 

way  a  drive-well  is  sunk.  The  pipe  is  divided  into  8  foot  sec- 
tions and  driven  with  a  plug  in  the  top  end.  Every  2  feet, 
4  feet,  or  8  feet,  the  plug  is  removed  and  the  pipe  cleaned  out 
with  a  sand  pump.  Water  is  used  to  loosen  up  the  materials 
in  the  pipe.  By  examining  the  materials  thus  removed  a 
record  is  made  of  the  bottom.  It  is  a  good  plan  to  empty  the 
pump  each  time  into  a  tall  glass  jar,  the  water  being  drained  off. 
The  exact  composition  of  the  materials  may  then  be  ascertained. 
From  time  to  time  the  pipe  will  become  plugged  with  stone, 
in  which  case  a  drill  such  as  shown  in  Fig.  115  is  screwed  into  a 
gas  pipe  and  two  men,  using  it  as  a  churn  drill,  drill  out  the 
obstruction. 

The  driver  used  is  usually  made  in  the  form  of  a  small  pile 
driver,  a  heavy  section  of  some  hard-wood  tree  being  used  for 
the  hammer.  The  hammer  may  be  lifted  by  man  power.  "Where 
only  a  few  holes  are  required  a  2  inch  pipe  may  be  driven  with 
a  heavy  post  maul. 

Much  may  be  learned  of  the  character  of  the  substratas  by 
sounding  with  a  f-inch  round  iron  rod,  and  the  engineer  should 
never  be  without  such  a  rod  when  making  a  hasty  preliminary 
inspection.  Only  a  year  ago  the  author  learned  this  at  a  cost 

of  about  $6000.     After  the  contract  was  secured,  a  little  £-inch 

_. 

rod  showed  that  where  it  was  without  a  doubt  solid  granite, 
the  bottom  dropped  down  14  feet,  making  much  more  ex- 
cavation necessary  than  had  been  figured  on,  and  necessitating 
the  building  of  more  dam. 

By  listening  to  the  rod  you  can  tell  whether  any  rock  struck 
is  solid  or  only  a  boulder. 

For  most  soft  soils  a  common  2-inch  wood  auger  having  a 
auger  handle,  or,  for  deep  boring,  a  handle  several  feet  long, 
is  handy  for  sounding.  There  are  several  earth  augers  on  the 
market,  but  for  soft  loams  and  clay  a  common  auger  is  good. 

In  this  manner  one  or  two  men  can  sound  over  a  large  area. 

FLOWAGE  HEIGHT. 

When  a  dam  is  to  be  built  it  becomes  a  question  of  great 
moment,  just  how  high  the  water  will  be  raised  at  different 
points  above  the  dam.  There  may  be  a  city  up  the  river  whose 
drainage  rights  must  not  be  affected,  or  there  may  be  another 
water  power  above  the  proposed  dam  whose  tail  water  limits 


RECONNAISSANCE  OF  WATER  POWER.  59 

the  height  of  the  proposed  dam.  In  these  cases  it  must  be  known 
what  the  flowage  height  will  be. 

Water  flowing  in  the  stream  obeys  the  same  laws  as  when 
flowing  in  a  canal  or  penstock.  It  merely  becomes  a  greater 
question  of  judgment  in  selecting  the  coefficient  of  roughness. 

The  first  step  is  to  go  over  the  reservoir  with  a  competent 
surveyor  and  take  accurate  profiles  of  the  cross-section  similar  to 
Fig.  48,  say  at  half-mile  intervals.  Here  A  B  is  the  assumed 
elevation  of  the  water  when  backed  up  by  the  dam,  C  D  is  a 
line  on  the  exact  level  of  the  dam's  crest,  E  F  is  the  level  of 
the  water  in  the  river  at  the  particular  section  before  the  dam 
is  built.  While  on  the  ground  decide  about  what  the  coefficient 
of  roughness  will  be,  making  allowance  for  bends  in  the  river, 
undulating  ground,  stumpages,  etc. 


f/J 


FIG.  48. 

The  fall  F  in  feet  between  any  two  points  along  the  stream 
above  the  dam  can  be  found  from  the  formula 


F   = 


wherein  F  is  the  fall  between  two  consecutive  points  where 
the  section  of  the  river  has  been  determined,  v  is  the  velocity 
of  the  stream  in  feet  per  second,  D  is  the  distance  in  feet  be- 
tween the  points,  C,  a  coefficient  depending  upon  the  ratio  of 
the  wet  perimeter  to  the  cross-section  of  the  stream  and  r  is 
the  mean  hydraulic  radius. 


wherein  Q  is  the  cubic  feet  of  water  flowing  per  second,  and  A 
is  the  area  of  the  cross-section  in  square  feet. 


t>0  HYDROELECTRIC  PLANTS. 

C  may  be  taken  from  the  table  given  below. 

,4 
r-=p- 

wherein  P  is  the  length  of  the  wet  perimeter. 

The  area  A  =  A  B  F  G  E.  can  be  estimated  from  the  pro- 
file curves  of  the  cross-section  at  the  point  in  question. 

Taking  the  profiles  of  the  cross-sections  every  half  mile  and 
solving  for  F  in  the  above  formula  a  curve  of  flowage  height,  F 
can  be  plotted. 

EXAMPLE. — A  river  having  a  flow  of  100,000  cubic  feet  per 
minute  is  to  be  dammed  with  a  12-foot  dam.  At  one  mile 
intervals  the  sections  1,  2,  3,  etc.,  are  taken  each  at  the  middle 
of  the  interval. 

Fig.  49  shows  the  section  one-half  mile  above  the  dam.     For 

TABLE  XIV. 

VALUES  FOR  C  COMMONLY  USED  BY  ENGINEERS. 
For  rivers,  and  canals  in  earth.     Fairly  regular. 
For  values  of  r  less  than  0.5 
u         «       "«  from 


han  0  5 

c 

-  30 

5  to  1 

C 

45 

1  "  2 

c 

55 

2  "  3 

c 

65 

3  "  4  

..  ..  c 

=  80 

4  "10  
30  "75.  . 

c 
.  .c 

=  100 
=  125 

the  first  mile  there  should  not  be  more  than  J-inch  fall,  so  A  B 
will  be  assumed  to  be  on  the  same  level  as  the  top  of  the  dam 
C  D.  With  a  planimeter,  or  otherwise,  the  area  A  =  4800 
square  feet  may  be  found.  The  wet  perimeter  P  =  480  feet, 

therefore  =  hydraulic  mean  radius  =  r  =  10.       From  Ta- 

ble XIV  C  would  be  100. 

cu.  it.  per  min. 
"4X60 

100,000 


4800X60 


=  .0347.     D  =  5280. 


RECONNAISSANCE  OF  WATER  POWER.  61 

'  -          - 

Profile  2  (Fig.  50)  is  located  a  mile  above  the  first  section 
and  1J  miles  above  the  dam.  Profiting  by  the  first  calculations 
A  B  is  placed  one  inch  above  C  D  (Fig.  48)  the  area  A  then  = 

100  000 
2600  square  feet  and  r  =  3.24,  D  =  5280,  v  =-  ™-        -  .64. 


C 


*>  H$sr=«— 


FIG.  50. 

and  so  on  with  all  the  sections  taken.  When  a  section  is  reached 
where  the  area  A  divided  into  fhe  flow  Q  gives  exactly  the 
same  velocity  as  that  found  in  the  stream  at  that  section  before 
the  dam  is  built,  we  know  that  we  are  where  the  dam  does  not 
affect  the  flow  at  all.  In  other  words  the  line  A  B  coincides 
with  the  normal  surface  of  the  water  in  the  river  at  that  point 
before  the  building  of  the  dam. 

COST  OF  SURVEYS. 

The  cost  of  a  survey  depends  entirely  on  the  density  of  under- 
brush, and  forests,  on  the  variation  of  levels  and  on  the  weather. 
Where  it  is  only  desired  to  get  an  approximate  and  hasty 


62  HYDROELECTRIC  PLANTS. 

level  showing  the  possible  head  obtainable  a  level  may  be  run 
without  checking  back,  for  about  $2  per  mile.  More  accurate 
levels  such  as  would  be  used  for  the  basis  of  an  investment, 
would  cost  about  $5  per  mile.  Precise  levels  will  cost  $20  to 
$30  per  mile. 

A  fairly  accurate  survey  of  the  overflowed  land  can  be  made 
for  from  $0.25  to  $0.50  per  acre.  This  includes  running  the 
levels  and  staking  out  the  high  water  level. 

Topographical  surveys  with  about  50  foot  contour  intervals 
will  cost,  for  densely  wooded  and  irregular  surface,  about  $200 
per  square  mile,  for  more  open  country  about  $80  to  $90,  and 
for  extensive  valleys,  bare  of  all  brush  and  trees  and  with 
gently  sloping  sides,  about  $50. 

The  same  surveys  with  5-foot  intervals  and  very  precisely 
made,  may  cost  from  $1000  to  $2000  per  square  mile. 

ENGINEER'S  REPORT. 

• 

GOVERNMENT    REPORTS. 

Great  importance  is  attached  by  all  capitalists  to  the  reports 
of  the  Government.  It  is  the  only  unbiased  report  they  have 
to  rely  upon.  It  is  therefore  well  to  give  the  Government 
reports  a  prominent  place.  If  these  reports,  as  is  often  the, 
case,  give  a  minimum  flow  which  there  is  reason  to  believe  is 
too  small  or  too  large,  every  effort  should  be  made  to  obtain 
from  the  office  of  Hydrography  a  detailed  description  of  exactly 
how  the  measurements  were  taken.  A  visit  to  the  gauging 
station  may  be  necessary  to  determine  the  value  of  the  reports. 

All  the  topographical  maps  prepared  by  the  department,  re- 
lating to  the  drainage  area  should  be  procured.  The  Weather 
Bureau  of  the  Department  of  Agriculture  should  be  consulted 
and  the  rainfall  for  the  driest  year  in  ten  tabulated  and  the 
average  taken  as  in  Table  XIII.  It  is  also  a  good  plan  to  prepare 
curves  showing  the  rainfall  (average)  for  each  month  on  the 
whole  drainage  area  for,  say,  ten  years. 

The  run-off  reports  furnish  data  for  another  curve  showing 
the  average  run-off  over  a  long  .period. 

ENGINEER'S  MEASUREMENTS. 

(1)  From  the  measurements  made  by  the  engineer  curves 
are  plotted  showing  the  run-off  for  as  long  as  they  were  taken. 


RECONNAISSANCE  OF  WATER  POWER. 


63 


TABLE  XV 
RUN-OFF  AND  XV.AIN  FALL  DATA. 


Branch  of  River 
to  be  developed 

Run-off  of  Similar  River, 
cu.  it.  per  sec.  per  sq.  mile. 

Ratio. 
f 
b 

Rainfall 
inches. 

Run-off 
cu.  ft.  per  sec. 
per  sq.  mile. 

Ratio 
b 
a 

Sta  Y 

StaZ 

*+_'  -  * 
2          T 

Month. 

(a) 

80 

(O 

(d) 

w 

(/) 

(g) 

June  

2.70 

2.420 

0.896 

0.56 

0.46 

0.510 

0.211 

July  

6.75 

5.854 

0.807 

0.44 

0.47 

0.455 

0.078 

August  .... 

0.94 

0.818 

0.870 

0.27 

0.31 

0.290 

0.356 

TABLE  XVI. 
RUN-OFF  AND  RAIN  FALL  DATA.     (DRY  YEAR). 


Branch  of  River 
to  be  Developed. 

Run-off  of  River 
to  be  Developed. 

Rainfall 
dry  year, 
inches. 

Run-off. 
h  Xc  =  * 

Cu.  ft.  per  sec. 
per  sq.  mile. 
i  Xg  =  j 

Cu.  ft.  per  sec. 
per  570  sq.  miles. 
570  X;  =  k. 

Month. 

0b) 

<«) 

(/) 

(« 

June  

1.67 

1.496 

0.315 

179.55 

July  

3.88 

3.364 

0.261 

148.77 

August  .... 

3.88 

3.364 

0.261 

148.77 

TABLE  XVII. 
RESERVOIR  EVAPORATION. 


inches. 

Cubic  feet  corresponding 
to  area  15  sq.  miles, 
area  Xl  =  m 

V) 

(m) 

6.10 

212,572,800 

6.90 

240,451,200 

5.60 

195,148,800 

TABLE  XVIII. 
WATER  FOR  MINIMUM  YEAR 


Total  Run-off, 
sec.  Xk  =  « 

Power  Draught 
@  400  cu.  ft.  per  sec. 

sec.  X400  =  0 

Total  Draught 

o  +  m  =  p 

Net  Volume 
cu.  ft. 

n-p  =  q 

Month. 
June. 

(K) 
465  393  600 

(o) 
1  036  800  000 

(P} 
1  249  372  800 

(<?) 
783  979  200 

July  
August..  .  . 

398,465,600 
1,548,061,400 

1,071,360,000 
1,071,360,000 

1,311,811,200 
1,130,601,600 

—913,345,600 
+  417.459,800 

64  HYDROELECTRIC  PLANTS. 

(2)  A  profile  of  the  river  bed  at  the  site  of  the  dam  is  pre- 
pared   showing    all   the    information    possible    relative   to   the 
proposition.     Each  boring  made  to  determine  the  character  of 
the  bottom  must  be  indicated.     A  plan  view  showing  the  loca- 
tion of  the  borings,  contour  lines,  etc.,  should  also  be  shown. 

(3)  A  contour  map   of  the  entire   drainage   area  should  be 
made  showing  not  only  the  overflowed  area,  but  also  the  loca- 
tion and  name  of  each  piece  of  land  affected. 

(4)  Where  the  contour  map  is  made  a  drawing  showing  the 
levels  from  the  dam  to  the  end  of  the  reservoir  will  not  be  re- 
quired, otherwise  it  will. 

(5)  Several  good  photographs  should  be  taken  showing  im- 
portant objects,   especially  both  banks  at  the  site  of  the  dam. 
These  can  be  used  for  the  prospectus. 

When  there  are  no  run-off  reports  for  the  river,  which  is  under 
consideration,  the  best  plan  is  to  select  some  river  having  a 
similar  drainage  basin  and  situated  in  about  the  same  part  of 
the  country,  for  which  reports  have  been  prepared,  and  use 
these  reports  as  outlined  below  to  determine  the  run  off  of  the 
river  to  be  developed. 

TABLE  XIX. 

APPROXIMATE   EFFICIENCIES    USED    IN    ESTIMATING   THE    NET* 
POWER  AVAILABLE. 

Generators 95%  4z>  90     %  net. 

Step-up  Transformers .  .  .97%  92. 1%    " 

Transmission  line 95%  87.5%   " 

Step  down  Transformers 97%  84 . 6%    " 

Distribution  to  Sub-stations 93%  79 . 0%    " 

Rotary  Converters 90%  71 . 1%    " 

Some  branch  of  the  river  to  be  developed  for  which  rainfall 
data  is  available,  is  selected  and  the  run-off  measured  for  each 
month.  The  ratio  between  run-off  and  rainfall  being  estab- 
lished for  this  branch,  the  rainfall  for  the  driest  year  is  multi- 
plied by  this  ratio  in  order  to  obtain  the  run-off  of  the  branch. 

At  the  same  time  the  run-off  of  this  branch  is  compared  with 
that  of  the  similar  river,  the  average  of  two  gauging  stations 
y  and  Z  being  taken,  and  another  ratio  determined-  then  mul- 
tiplying the  flow  of  the  branch  for  the  dry  year  by  this  second 
ratio  the  approximate  flow  of  the  river  is  obtained. 


RECONNAISSANCE  OF  WATER  POWER.  65 

Tables  XV  to  XVIII  show  the  method  of  computing  the  ap- 
proximate run-off  of  a  river  when  that  of  a  similar  river  is 
known,  the  evaporation  being  taken  into  account.  From 
these  four  tables  curves  may  be  plotted  showing  the  level  of 
the  water  in  the  reservoir  each  month  for  one  or  more  years. 
Two  of  the  driest  years  may  be  taken. 

Another  table  may  be  prepared  in  connection  with  the  ones 
given  herewith,  which  will  show  the  area  of  the  reservoir  for 
every  foot  of  elevation  between  the  points  of  maximum  and 
minimum  head. 

FORM   OF  REPORT. 

Having  compiled  the  foregoing  data  the  report  might  take 
the  following  form,  subject  to  those  modifications  which  each 
particular  proposition  will  make  necessary: 
Introduction. 

DEAR  SIR:  I  beg  to  submit,  etc. 
General  Description. 

The  site  of  the  proposed  development,  etc. 
Flow  of  the  Stream. 

Curves  relating  to  the  measurements  made  by  engineers  and 
Government.  Table  developing  the  "  ratio  "  of  run-off. 

Table  giving  run-off  for  stream  under  consideration. 

Table  giving  evaporation.      Table  giving  net  run -off  for  use 
through  turbines,  etc. 
Power  Capacity  of  the  Stream. 

Table  giving  the  efficiencies  of  each  mechanism  commencing 
with  the  turbine  and  ending  at  the  point  where  power  is  sold. 

Curves  showing  the  delivered  power  for  each  year  when  meas- 
urements were  taken. 
Market  for  the  Power. 

Table  or  curves  showing  the  load  of  the  various  customers, 
the  rate  of  increase  of  the  power  used  by  these  companies  for 
a  few  years  back  and  the  estimated  power  which  they  will  use 
for  a  number  of  years  in  the  future.  Curve  showing  the  char- 
acter of  the  probable  daily  load. 
Auxiliary  Steam  Operation. 

Curve  showing  the  power  in  the  river  during  a  dry  year  and 
a  shaded  portion  showing  the  part  of  the  load  which  would 
have  to  be  carried  by  steam.  Table  showing  the  per  cent,  of 


66 


HYDROELECTRIC  PLANTS 


TABLE  XX. 

MAINTENANCE  AND  DEPRECIATION. 

Maintenance.  Depreciation. 

Buildings 1.0  1.0 

Auxiliary  Mechanism 1.0  1.0 

Exciters 5.0  2.0 

Storage  Battery 5.0  2.0 

Generators 2.0  5.0 

Transformers 2.0  1.0 

Station  Wiring 1.0  5.0 

Lightning  Protection 15.0  0.8 

Transmission  Line 10.0  0.0 

Turbines 3.5  18.0 

Gates  and  Racks . .  1.0  7.5 


TABLE  XX-A. 
COST  OF  OPERATING  STEAM  POWER. 


Year  to  which  figures  are  assumed  to  apply 
Total  yearly  demand  at  (         )  per  kw-hr. 
Average  output  rate  for  year  kw  
Average  output  rate  for  year  (max.  day)  kw 
Engine  and  generating  capacity  kept  ready 
for  use  (h  p   nom  )  

1905 

1910 

1915 

n 

Boilers  retained  in  station  
Per  cent,  of  demand  required  by  steam  
Total  output  by  steam  for  year  kw-hr  
Cost  of  coal  for  actual  running  at   (         ) 
per  kw-hr  .  .            .    .        . 

Cost  of  coal  for  banking  (at  10,  8,  6,  4  and 
3%).. 

Emergency  labor  (.0075,  0070,  .004  cts.  per 
kw-hr. 

Permanent  force  at  station 

Maintenance  of  boilers  at  80c.  per  h.p.  .  .  . 
Maintenance  of  engine  at  60c.  per  h.p.  .  .  . 
Total  cost  of  operating  steam  auxiliary  
Cost  per  kw-hr.  output  

RECONNAISSANCE  OF  WATER  POWER.  67 

steam  operation  based  on  the  load  for  a  few  years  back  and 
covering  a  number  of  years  in  the  future. 
Back  Water  Conditions. 

Full  description  with  curves  showing  the  duration,  etc. 
Pondage. 

Table  giving  cubical  contents  of  reservoir  for  each  foot  of 
depth  the  pond  will  be  drawn  down. 

Curves  of  the  power  with  shaded  portion  showing  the  part 
of  the  load  the  stored-up  water  will  carry  (similar  to  the  steam 
load). 
Detailed  Description  of  the  Work. 

Power   house,    transmission   lines,   canals,   head   gates,    dam, 
miscellaneous. 
Estimates  of  Cost  of  Construction. 

Dam,  power  house,  etc. 
Operating  Charges. 
Maintenance  and  Depreciation. 

Table  showing  per  cent,  of  depreciation  and  maintenance  on 
each  detail  of  the  work;  labor  and  small  supplies.  (Table  XX.) 

Cost  of  operation  of  auxiliary  power,  taxes,  interest,  office 
expenses,  etc.  (Table  XXA.) 

Revenue. 

Full  reasons  for  believing  power  can  be  sold  at  the  given  price, 
etc. 
Summary. 

Gross  receipts .....$ 

Operating  expenses $.  .  . 

Net  profit $ 

Interest  on  the  investment $ 

As  an  appendix  the  report  may  contain  small  scale  drawings 
of  the  dam,  power  house,  etc.  Photographs  made  from  the 
tracings  are  good  for  this  purpose. 


CHAPTER  IV. 
MATERIALS. 

Before  taking  up  hydraulic  construction  it  is  well  to  consider 
the  relative  suitability  of  the  various  materials.  Many  times 
structures  are  subjected  to  alternate  exposure  of  air  and  water, 
and  this  condition  is  a  severe  one  which  comparatively  few 
materials  can  successfully  withstand. 

WOOD. 

It  is  a  well  known  fact  that  practically  all  woods,  if  submerged 
in  water,  will  be  preserved  from  decay.  Therefore,  where  pos- 
sible, all  timber  should  be  submerged.  The  condition  most 
conducive  to  decay  is  that  of  continual  change  from  dry  to  wet 
and  wet  to  dry.  The  most  rapid  decay  ever  witnessed  by  the 
writer  was  where  the  posts  of  a  flume  came  in  contact  wit^ 
gumbo,  a  soil  common  alcr-g  western  rivers,  and  at  the  water 
line.  In  this  case  8x8-inch  pine  timber  lasted  only  six  years. 
Ordinarily,  pine  timber  under  most  unfavorable  conditions,  lasts 
from  eight  to  twelve  years. 

With  few  exceptions,  all  timber  decays  first  in  the  sapwood. 
Hence  specifications  should  exclude  the  sap.  Certain  woods 
are  wholly  unsuited  for  work  in  contact  with  varying  degrees  of 
moisture.  Some  of  these  are  as  follows:  Elm  (except  rock  elm), 
soft  maple,  willow,  poplar,  baswood,  all  oaks  (except  white, 
pin  oak  and  live  oak),  spruce,  pine  and  hemlock. 

Among  the  best,  and  in  order  of  superiority  for  such  work, 
are  the  following:  Texas  and  Oregon  fir,  red  and  white  cedar, 
"  Hart  "  yellow  pine,  live  oak,  white  oak,  pin  oak,  white  pine 
(free  from  sap),  beech,  spruce  pine,  tamerack  and  hemlock. 

Hemlock  is  given  in  both  lists,  as  it  is  on  the  border-line. 
The  upland  hemlock  lasts  fairly  well.  Yellow  pine,  when  free 
from  sap,  makes  a  very  satisfactory  material,  and  the  cost  is 
moderate.  For  most  rivers,  white  oak  makes  good  timber,  yet 

68 


MATERIALS.  69 

there  are  cases  on  record  where  the  acid  in  the  oak  was  attacked 
by  some  chemical  in  the  water  and  the  timber  destroyed  in  a  few 
years. 

No  matter  what  wood  is  used,  or  how  well  it  may  be  dry-seas- 
oned, after  it  has  been  exposed  to  water  for  a  few  years,  it  will 
shrink.  Of  course,  the  more  thoroughly  it  is  dried,  the  less  will 
be  the  contraction.  The  first  effect  of  the  water  is  to  swell  the 
wood.  Plank,  when  continually  wet  on  one  side  so  that  the 
wood  is  saturated,  will  last  indefinitely. 

Soft  wood  is  worn  away  less  rapidly  by  running  water  than  is 
hard  wood. 

METALS. 

Among  the  cheaper  metals,  cast  iron  resists  the  corroding 
effect  of  water  the  best.  Steel  corrodes  much  more  rapidly. 
All  metals  corrode  more  rapidly  when  exposed  to  running  water, 
and  the  higher  the  velocity  the  more  rapid  the  corrosion.  Steel 
penstocks  wear  away  rapidly  and  become  rough,  increasing  the 
coefficient  of  friction.  Nothing  thinner  than  J-inch  should  be 
used. 

For  work  under  high  heads  such  as  several  hundred  feet  or 
more  the  water  frequently  bores  holes  through  cast  iron  turbine 
runners,  and  nothing  but  bronze  should  be  used  for  such  parts. 

CEMENT  AND  CONCRETE. 

Five  years  ago  we  were  in  the  steel  age,  but  to-day  it  is  the 
concrete-steel  age.  Bridges  on  all  the  great  railways  were  then 
built  of  steel;  to-day  the  best  practice  points  to  the  concrete- 
steel  bridge. 

The  price  of  steel  remains  at  about  the  same  figure.  The 
price  of  timber  is  steadily  going  up,  having  increased  fully  50 
per  cent,  in  10  years.  Interest  on  money  is  steadily  going  down. 
Cement  is  each  year  getting  cheaper.  The  tendency  of  the  limes 
is  toward  more  permanent  construction.  These  facts  have  con- 
tributed to  usher  in  the  concrete-steel  age.  The  characteristics 
of  steel  have  been  thoroughly  worked  out.  It  has  high  tensile 
strength,  is  quite  flexible,  has  good  elasticity,  and  is  uniform 
in  all  its  features. 

But  cement  is  not  so  well  understood.  In  fact,  there  are  as 
many  ideas  concerning  its  proper  combinations  as  there  are 
engineers. 


70  HYDROELECTRIC  PLANTS. 

There  are  two  distinct  kinds  of  cement,  natural  or  Rosendale, 
and  Portland.  Some  of  the  largest  works  have  used  Rosendale, 
as,  for  instance,  the  Croton  dam,  but  in  the  last  few  years  Port- 
land cement  has  been  made  in  the  United  States  in  much  larger 
quantities  and  of  such  splendid  quality  that  the  use  of  any  other 
is  no  longer  advisable. 

•  Frost  affects  Rosendale  cement,  and  under  no  circumstances 
should  it  be  used  when  frost  can  reach  it.  For  the  interior 
portions  of  large  monolithic  dams  and  where  it  is  desired  to  save 
a  few  dollars  (a  questionable  policy)  Rosendale  might  be  used. 
The  price  of  Portland  has  now  gained  a  point  where,  on  account 
of  its  superior  strength,  there  is  no  real  economy  in  the  use  of 
cheap  cement. 

There  are  innumerable  brands  of  cement  made  in  the  United 
States  to-day,  most  of  which  are  equal  to  the  English  and  Ger- 
man cements.  Among  the  best  might  be  mentioned  Giant 
Portland,  Lehigh,  and  Atlas. 

TESTING. 

All  cement,  no  matter  of  what  brand,  should  be  tested  before 
being  used  on  important  works. 

The  following  tests  are  those  recommended  by  the  American1 
Society   of  Civil   Engineers  in    1902*,   and  which   are  without 
doubt  the  most  authorative  we  have  to-day. 

Sampling. 

Selection  of  Sample. — The  selection  of  the  sample  for  testing 
is  a  detail  that  must  be  left  to  the  discretion  of  the  engineer; 
the  number  and  the  quantity  to  be  taken  from  each  package 
will  depend  largely  on  the  importance  of  the  work,  the  number 
of  tests  to  be  made  and  the  facilities  for  making  them.  The 
sample  shall  be  a  fair  average  of  the  contents  of  the  package; 
it  is  recommended  that,  where  conditions  permit,  one  barrel  in 
every  10  should  be  sampled.  All  samples  should  be  passed 
through  a  sieve  having  20  meshes  per  linear  inch,  in  order  to 
break  up  lumps  and  remove  foreign  material;  this  is  also  a  very 
effective  method  for  mixing  them  together  in  order  to  obtain 
an  average.  For  determining  the  characteristics  of  a  shipment 

*Report  of  the  American  Society  of  Civil  Engineers'  Committee  on 
Uniform  tests  of  Cement. 


MATERIALS.  71 

of  cement,  the  individual  samples  may  be  mixed  and  the  average 
tested;  where  time  will  permit,  however,  it  is  recommended  that 
they  be  tested  separately. 

Method  of  Sampling. — Cement  in  barrels  should  be  sampled 
through  a  hole  made  in  the  center  of  one  of  the  staves,  midway 
between  the  heads,  or  in  the  head,  by  means  of  an  auger  or 
sampling  iron  similar  to  that  used  by  sugar  inspectors.  If  in 
bags  it  should  be  taken  from  surface  to  center. 

Chemical    A  nalysis . 

Significance. — Chemical  analysis  may  render  valuable  service 
in  the  detection  of  adulteration  of  cement  with  considerable 
amounts  of  inert  material,  such  as  slag  or  ground  limestone. 
It  is  of  use,  also  in  determining  whether  certain  constituents, 
believed  to  be  harmful  when  in  excess  of  a  -certain  percentage, 
as  magnesia  and  sulphuric  anhydride,  are  present  in  inadmis- 
sible proportions.  While  not  recommending  a  definite  limit  for 
these  impurities,  the  committee  would  suggest  that  the  most 
recent  and  reliable  evidence  appears  to  indicate  that  for  Portland 
cement  magnesia  to  the  amount  of  5  per  cent,  and  sulphuric 
anhydride  to  the  amount  of  1.75  per  cent.,  may  safely  be  con- 
sidered harmless. 

The  determination  of  the  principal  constituents  of  cement — 
silica,  alumina,  iron  oxide  and  lime — is  not  conclusive  as  an 
indication  of  quality.  Faulty  character  of  cement  results  more 
frequently  from  imperfect  preparation  of  the  raw  material  or 
defective  burning  than  from  incorrect  proportions  of  the  con- 
stituents. Cement  made  from  very  finely-ground  material,  and 
thoroughly  burned,  may  contain  much  more  lime  than  the 
amount  usually  present  and  still  be  perfectly  sound.  On  the 
other  hand,  cements  low  in  lime  may,  on  account  of  careless 
preparation  of  the  raw  materials,  be  of  dangerous  character. 
Further,  the  ash  of  the  fuel  used  in  burning  may  so  greatly 
modify  the  composition  of  the  product  as  largely  to  destroy  the 
significance  of  the  results  of  analysis. 

Method. — As  a  method  to  be  followed  for  the  analysis  of  cement 
that  proposed  by  the  Committee  on  Uniformity  in  the  Analysis 
of  Materials  for  the  Portland  Cement  Industry,  of  the  New 
York  Section  of  the  Society  for  Chemical  Industry,  and  pub- 
lished in  the  Journal  of  the  Society,  for  January  15,  1902,  is 
recommended. 


72 


HYDROELECTRIC  PLANTS. 


Specific  Gravity. 

Significance.— The  specific  gravity  of  cement  is  lowered  by 
underburning,  adulteration  and  hydra tion,  but  the  adulteration 
must  be  in  considerable  quantity  to  effect  the  results  appre- 
ciably. Inasmuch  as  the  difference  in  specific  gravity  are  usually 
very  small,  great  care  must  be  exercised  in  making  the  deter- 
mination. When  properly  made,  this  test  affords  a  quick  check 
for  underburning  or  adulteration. 

Apparatus  and  Method. — The  determination  of  specific  gravity 
is  most  conveniently  made  with  Le  Chatelier's  apparatus.  This 
consists  of  a  flask  (D),  Fig.  51,  of  120  cubic  centimeters  (7.32 


FIG.  51. 

cubic  inches)  capacity,  the  neck  of  which  is  about  20  centi- 
meters (7.87  inches)  long;  in  the  middle  of  this  neck  is  a  bulb 
(C),  above  and  below  which  are  two  marks  (E)  and  (F) ;  the 
volume  between  these  marks  is  20  cubic  centimeters  (1.22 
cubic  inches).  The  neck  has  a  diameter  of  about  9  millimeters 
(0.35  inch),  and  is  graduated  into  1-10  cubic  centimeters  above 
the  bulb.  Benzine  (62°  Baume  naphtha),  or  kerosene  free 
from  water,  should  be  used  in  making  the  determination.  The 
specific  gravity  can  be  determined  in  two  ways: 

1.  The  flask  is  filled  with  liquid  to  the  lower  mark  (E),  and 
64  grains  (2.25  ounces)  of  powder,  previously  dried  at  100°  C. 


MATERIALS.  73 

(212°  F.)  and  cooled  to  the  temperature  of  this  liquid,  is  gradually 
introduced  through  the  funnel  (B)  [the  stem  of  which  extends 
into  the  flask  to  the  top  of  the  bulb  (C)],  until  the  upper  mark 
(F)  is  reached.  The  difference  in  weight  between  the  cement 
remaining  and  the  original  quantity  (64  grains)  is  the  weight 
which  has  displaced  20  cubic  centimeters. 

2.  The  whole  quantity  of  the  powder  is  introduced,  and  the 
level  of  the  liquid  rises  to  some  division  of  the  graduated  neck. 
This  reading  plus  20  cubic  centimeters  is  the  volume  displaced 
by  64  grains  of  the  powder. 

The  specific  gravity  is  then  obtained  from  the  formula: 

„       .„  .  Weight  of  cement 

Specific  gravity  =  A.     , 

Displaced  volume. 

The  flask,  during  the  operation,  is  kept  immersed  in  water 
in  a  jar  (A),  in  order  to  avoid  variations  in  the  temperature  of 
the  liquid.  The  results  should  agree  within  0.01. 

A  convenient  method  for  cleaning  the  apparatus  is  as  follows : 
The  flask  is  inverted  over  a  large  vessel,  preferably  a  glass  jar 
and  shaken  vertically  until  the  liquid  starts  to  flow  freely;  it  is 
then  held  still  in  a  vertical  position  until  empty ;  the  remaining 
traces  of  cement  can  be  removed  in  a  similar  manner  by  pouring 
into  the  flask  a  small  quantity  of  clean  liquid  and  repeating  the 
operation.  More  accurate  determinations  may  be 'made  with 
the  picnometer. 

Fineness. 

Significance. — It  is  generally  accepted  that  the  coarser  par- 
ticles in  cement  are  practically  inert,  and  it  is  only  the  extremely 
fine  powder  that  possesses  adhesive  or  cementing  qualities. 
The  more  finely  cement  is  pulverized,  all  other  conditions  being 
the  same,  the  more  sand  it  will  carry  and  produce  a  mortar  of  a 
given  strength.  The  degree  of  final  pulverization  which  the 
cement  receives  at  the  place  of  manufacture  is  ascertained  by 
measuring  the  residue  retained  on  certain  sieves.  Those  known 
as  the  No.  100  and  No.  200  sieves  are  recommended  for  this  pur- 
pose. 

Apparatus. — The  sieve  should  be  circular,  about  20  centimeters 
(7.87  inches)  in  diameter,  6  centimeters  (2.36  inches)  high,  and 
provided  with  a  pan  5  centimeters  (1.97  inches)  deep,  and  a 
cover. 


74  HYDROELECTRIC  PLANTS. 

The  wire  cloth  should  be  woven  (not  twilled)  from  brass  wire 
having  the  following  diameters:  No.  100,  0.0045  inch;  No.  200, 
0.0324  inch.  The  wire  cloth  should  be  mounted  on  the  frames 
without  distortion;  the  meshes  should  be  regular  in  spacing  and 
be  within  the  following  limits:  No.  100,  96  to  100  meshes  to  the 
linear  inch;  No.  200,  188  to  200  meshes  to  the  linear  inch.  Fifty 
grams  (1.76  ounces)  or  100  grains  (3.52  ounces)  should  be  used 
for  the  test,  and  dried  at  a  temperature  of  100°  C.  (212°  F.)  prior 
to  sieving. 

Method. — The  committee,  after  careful  investigation,  has 
reached  the  conclusion  that  mechanical  sieving  is  not  as  prac- 
tical or  efficient  as  hand  work,  and,  therefore,  recommends  the 
following  method:  The  thoroughly  dried  and  coarsely  screened 
sample  is  weighed  and  placed  on  the  No.  200  sieve,  which,  with 
pan  and  cover  attached,  is  held  in  one  hand  in  a  slightly  inclined 
position,  and  moved  forward  and  backward,  at  the  same  time 
striking  the  side  gently  with  the  palm  of  the  other  hand,  at  the 
rate  of  about  200  strokes  per  minute.  The  operation  is  con- 
tinued until  not  more  than  0.1  per  cent,  passes  through  after 
one  minute  of  continuous  sieving.  The  residue  is  weighed,  then 
placed  on  the  No.  100  sieve  and  the  operation  repeated.  The  work 
may  be  expedited  by  placing  in  the  sieve  a  small  quantity  oia 
large  shot.  .  The  result  should  be  reported  to  the  nearest  tenth 
of  1  per  cent. 

Normal  Consistency. 

Significance. — The  use  of  a  proper  percentage  of  water  in 
making  the  pastes*  from  which  pats,  tests  of  setting  and  bri- 
quettes are  made,  is  exceedingly  important,  and  affects  vitally 
the  results  obtained.  The  determination  consists  in  measuring 
the  amount  of  water  required  to  reduce  the  cement  to  a  given 
state  of  plasticity,  or  to  what  is  usually  designated  the  normal 
consistency.  Various  methods  have  been  proposed  for  making 
this  determination,  none  of  which  have  been  found  entirely 
satisfactory.  The  committee  recommends  the  following: 

Method:  Vicat  Needle  Apparatus. — This  consists  of  a  frame 
K,  Fig.  52,  bearing  a  movable  rod  L,  which  has  a  cap  A  at  one 
end,  and  at  the  other  end  a  cylinder  B,  1  centimeter  (0.39  inch 

*The  term  "  paste  "  is  used  in  this  report  to  designate  a  mixture  of 
cement  and  water,  and  the  word  "  mortar  "  a  mixture  of  cement,  sand 
and  water. 


MATERIALS. 


75 


in  diameter,  the  cap,  rod  and  cylinder  weighing  300  grains 
(10.57  ounces).  The  rod,  which  can  be  held  in  any  desired 
position  by  a  screw  jp,  carries  an  indicator,  which  moves  over  a 
scale  (graduated  to  centimeters)  attached  to  the  frame  K. 
The  paste  is  held  by  a  conical,  hard-rubber  ring  7,  7  centimeters 
(2.76  inches)  in  diameter  at  the  base,  4  centimeters  (1.57  inches) 
high,  resting  on  a  glass  plate  /,  10  centimeters  (3.94  inches) 
square. 

In  making  the  determination,  500  grains  (17.64  ounces)  of 
cement  are  kneeded  into  a  paste,  as  described  in  a  succeeding 
paragraph,  and  is  then  formed  into  a  ball  with  the  hands,  com- 


FIG.    52. 

pleting  the  operation  by  tossing  it  six  times  from  one  hand  to 
the  other,  maintained  6  inches  apart;  the  pall  is  then  pressed 
into  the  rubber  ring,  through  the  larger  opening,  smoothed  off 
and  placed  on  a  glass  plate  (on  its  large  end),  and  the  smaller 
end  smoothed  off  with  a  trowel;  the  paste,  confined  in  the  ring 
resting  on  the  plate,  is  placed  under  the  rod  bearing  the  cylinder 
which  is  brought  in  contact  with  the  surface  and  quickly  released. 
The  paste  is  of  normal  consistency  when  the  cylinder  penetrates 
to  a  point  in  the  mass  10  millimeters  (0.39  inch)  below  the  top 
of  the  ring.  Great  care  must  be  taken  to  fill  the  ring  exactly 
to  the  top. 

The  trial  pastes  are  made  with  varying  percentages  of  water 


76  HYDROELECTRIC  PLANTS. 

until  the  correct  consistency  is  obtained.  The  committee  be 
lieves  that  the  normal  consistency  should  produce  a  rather  wet 
paste,  since  this  consistency  tends  to  greater  uniformity  in  the 
mixing,  and  since  there  is  less  liability  of  compressing  the  bri- 
quettes during  the  molding.  Having  determined  in  this  manner 
the  proper  percentage  of  water  required  to  produce  a  neat  paste 
of  normal  consistency,  the  proper  percentage  required  for  the 
sand  mortars  is  obtained  from  an  empirical  formula.  The  com- 
mittee hopes  to  devise  such  a  formula.  The  subject  proves  to 
be  a  very  difficult  one,  and,  although  the  committee  has  given 
it  much  study,  it  is  not  yet  prepared  to  make  a  definite  recom- 
mendation. 

Time  of  Setting. 

Significance. — The  object  of  this  test  is  to  determine  the 
time  which  elapses  from  the  moment  water  is  added  until  the 
paste  ceases  to  be  fluid  and  plastic  (called  the  "  initial  set  "), 
and  also  the  time  required  for  it  to  acquire  a  certain  degree  of 
hardness  (called  the  "  final  "  or  "  hard  set.") 

The  former  of  these  is  the  more  important,  since,  with  the  com- 
mencement of  setting,  the  process  of  crystallization  or  harden- 
ing is  said  to  begin.  As  a  disturbance  of  this  process  may 
produce  a  loss  of  strength,  it  is  desirable  to  complete  the  opera- 
tion of  mixing  and  molding  or  incorporating  the  mortar  into 
the  work  before  the  cement  begins  to  set.  It  is  usual  to  measure 
arbitrarily  the  beginning  and  end  of  the  setting  by  the  pene- 
tration of  weighted  wires  of  given  diameters. 

Method. — For  this  purpose  the  Vicat  needle,  which  has  al- 
ready been  described,  should  be  used.  In  making  the  test, 
a  paste  of  normal  consistency  is  molded  and  placed  under  the 
rod  L,  Fig.  52;  the  cylinder  and  the  cap  A  are  replaced  by  the 
needle  H,  one  millimeter  (0.039  inches)  in  diameter,  and  the 
cap  D,  the  rod  L  with  cap  D  and  needle  //,  weighing  300  gr. 
(10.57  ounces).  The  needle  is  then  carefully  brought  in  con- 
tact with  the  surface  of  the  paste  and  quickly  released.  The 
setting  is  said  to  have  commenced  when  the  needle  ceases  to 
pass  a  point  five  millimeters  (0.20  inches)  above  the  upper 
surface  of  the  glass  plate,  and  is  said  to  have  terminated  the 
moment  the  needle  does  not  sink  visibly  into  the  mass. 

The  test  pieces  should  be  stored  in  moist  air  during  the  test ; 
this  is  accomplished  by  placing  them  on  a  rack  over  water 


MATERIALS. 


77 


contained  in  a  pan  and  covered  with  a  damp  cloth,  the  cloth  to 
be  kept  away  from  them  by  means  of  a  wire  screen;  or  they  may 
be  stored  in  a  moist  box  or  closet.  Care  should  be  taken  to 
keep  the  needle  clean,  as  the  collection  of  cement  on  the  sides 
of  the  needle  retards  the  penetration,  while  cement  on  the 
point  reduces  the  area  and  tends  to  increase  the  penetration* 
The  determination  of  the  time  of  setting  is  only  approximate, 
being  materially  affected  by  the  temperature  of  the  mixing 
water,  the  temperature  and  humidity  of  the  air  during  the 
test,  the  percentage  of  water  used,  and  the  amount  of  molding 
the  paste  receives. 


FIG.  53. 

Standard  Sand. 

The  committee  recognizes  the  grave  objections  to  the  standard 
quartz  now  generally  used,  especially  on  account  of  its  high 
percentage  of  voids,  the  difficulty  of  compacting  in  the  molds, 
and  its  lack  of  uniformity ;  it  has  spent  much  time  in  investigat- 
ing the  various  natural  sands  which  appeared  to  be  available 
and  suitable  for  use.  For  the  present,  the  committee  recom- 
mends the  natural  sand  from  Ottawa,  111.,  screened  to  pass  a 
sieve  having  20  meshes  per  linear  inch  and  retained  on  a  sieve 
having  30  meshes  per  linear  inch;  the  wires  to  have  diameters 


78 


HYDROELECTRIC  PLANTS. 


of  0.0165  and  0.0112  inches,  respectively,  i.e.,  half  the  width 
of  the  opening  in  each  case.  The  Sandusky  Portland  Cement 
Co.,  of  Sandusky,  O.,  has  agreed  to  undertake  the  preparation  of 
this  sand,  and  to  furnish  it  at  a  price  only  sufficient  to  cover 
the  actual  cost  of  preparation. 

While  the  form  of  the  briquette  recommended  by  a  former 
committee  of  the  society  is  not  wholly  satisfactory,  this  com- 
mittee is  not  prepared  to  suggest  any  change,  other  than  round- 
ing off  the  corners  by  curves  of  J-inch  radius,  Fig.  53. 

Molds. 

The  molds  should  be  made  of  brass,  bronze  or  some  equally 
non-corrodible  material,  having  sufficient  metal  in  the  sides  to 


FIG.  54. 

prevent  spreading  during  molding.  Gang  molds,  which  permit 
molding  a  number  of  briquettes  at  one  time,  are  preferred  by 
many  to  single  molds;  since  the  greater  quantity  of  mortar  that 
can  be  mixed  tends  to  produce  greater  uniformity  in  the  re- 
sults. The  type  shown  in  Fig.  54  is  recommended.  The 
molds  should  be  wiped  with  an  oily  cloth  before  using. 

Mixing. 

All  proportions  should  be  stated  by  weight;  the  quantity  of 
water  to  be  used  should  be  stated  as  a  percentage  of  the  dry 


MATERIALS.  79 

material.  The  metric  system  is  recommended  because  of  the 
convenient  relation  of  the  gram  and  the  cubic  centimeter. 
The  temperature  of  the  room  and  the  mixing  water  should  be 
as  near  21°  C.  (70°  F.)  as  it  is  practicable  to  maintain  it.  The 
Sand  and  cement  should  be  thoroughly  mixed  dry.  The  mixing 
should  be  done  on  some  non-absorbing  surface,  preferably  plate 
glass.  If  the  mixing  must  be  done  on  an  absorbing  surface 
it  should  be  thoroughly  dampened  prior  to  use.  The  quantity 
of  material  to  be  mixed  at  one  time  depends  on  the  number  of 
test  pieces  to  be  made;  about  1000  gr.  (35.28  ounces)  makes  a 
convenient  quantity  to  mix,  especially  by  hand  methods. 

The  committee,  after  investigation  of  the  various  mechanical 
mixing  machines,  has  decided  not  to  recommend  any  machine 
that  has  thus  far  been  devised,  for  the  following  reasons:  (1) 
The  tendency  of  most  cement  is  to  "  ball  up  "  in  the  machine, 
thereby  preventing  the  working  of  it  into  a  homogeneous 
paste;  (2)  there  are  no  means  of  ascertaining  when  the  mixing 
is  complete  without  stopping  the  machine,  and  (3)  the  diffi- 
culty of  keeping  the  machine  clean. 

Method. — The  material  is  weighed  and  placed  on  the  mixing 
table,  and  a  crater  formed  in  the  center,  into  which  the  proper 
percentage  of  clean  water  is  poured;  the  material  on  the  outer 
edge  is  turned  into  the  crater  by  the  aid  of  a  trowel.  As  soon 
as  the  water  has  been  absorbed,  which  should  not  require  more 
than  one  minute,  the  operation  is  completed  by  vigorously 
kneading  with  the  hands  for  an  additional  1J  minutes,  the 
process  being  similar  to  that  used  in  kneading  dough.  A  sand- 
glass affords  a  convenient  guide  for  the  time  of  kneading. 
During  the  operation  of  mixing  the  hands  should  be  protected 
by  gloves,  preferably  of  rubber. 

Molding. 

Having  worked  the  paste  or  mortar  to  the  proper  consistency, 
it  is  at  once  placed  in  the  molds  by  hand.  The  committee  has 
been  unable  to  secure  satisfactory  results  with  the  present 
molding  machines;  the  operation  of  machine  molding  is  very 
slow,  and  the  present  types. permit  of  molding  but  one  briquette 
at  a  time,  and  are  not  practicable  with  the  pastes  or  mortars 
herein  recommended. 

Method. — The  molds  should  be  filled  at  once,  the  material 


80  HYDROELECTRIC  PLANTS. 

pressed  in  firmly  with  the  fingers  and  smoothed  off  with  a  trowel 
without  ramming;  the  material  should  be  heaped  up  on  the 
upper  surface  of  the  mold,  and,  in  smoothing  off,  the  trowel 
should  be  drawn  over  the  mold  in  such  a  manner  as  to  exert 
a  moderate  pressure  on  the  excess  material.  The  mold  should 
be  turned  over  and  the  operation  repeated.  A  check  upon  the 
uniformity  of  the  mixing  and  molding  is  afforded  by  weighing 
the  briquettes  just  prior  to  immersion,  or  upon  removal  from 
the  moist  closet.  Briquettes  which  vary  in  weight  more  than 
three  per  cent,  from  the  average  should  not  be  tested. 

Storage  of  the  Test  Pieces. 

During  the  first  24  hours  after  molding,  the  test  pieces  should 
be  kept  in  moist  air  to  prevent  them  from  drying  out.  A  moist 
closet  or  chamber  is  so  easily  devised  that  the  use  of  the  damp 
cloth  should  be  abandoned  if  possible.  Covering  the  test  pieces 
with  a  damp  cloth  is  objectionable,  as  commonly  used,  because 
the  cloth  may  dry  out  unequally,  and,  in  consequence,  all  the 
test  pieces  are  not  maintained  under  the  same  condition.  Where 
a  moist  closet  is  not  available  a  cloth  may  be  used  and  kept 
uniformly  wet  by  immersing' the  ends  in  water.  It  should  be 
kept  from  direct  contact  with  the  test  pieces  by  means  of  a  wire 
screen  or  some  similar  arrangement. 

\  moist  closet  consists  of  a  soapstone  or  slate  box,  or  a  metal- 
lined  wooden  box — the  metal  lining  being  covered  with  felt 
and  this  felt  kept  wet.  The  bottom  of  the  box  is  so  constructed 
as  to  hold  water,  the  sides  are  provided  with  cleats  for  holding 
glass  shelves  on  which  to  place  the  briquettes.  Care  should  be 
taken  to  keep  the  air  in  the  closet  uniformly  moist. 

After  24  hours  in  moist  air,  the  test  pieces  for  longer  periods 
of  time  should  be  immersed  in  water  maintained  as  near  21°  C. 
(70°  F.)  as  practicable;  they  may  be  stored  in  tanks  or  pans, 
which  should  be  of  non-corrodible  material. 

Tensile  Strength. 

The  tests  may  be  made  on  any  standard  machine.  A  solid 
metal  clip,  as  shown  in  Fig.  55,  is  recommended;  this  clip  is 
to  be  used  without  cushioning  at  the  points  of  contact  with 
the  test  specimen.  The  bearing  at  each  point  of  contact  should 
be  J-inch  wide,  and  the  distance  between  the  center  of  contact 
on  the  same  clip  should  be  1J  inches. 


MATERIALS. 


81 


Test  pieces  should  be  broken  as  soon  as  they  are  removed 
from  the  water.  Care  should  be  observed  in  centering  the 
briquettes  in  the  testing  machine,  as  cross-strains,  produced 
by  improper  centering,  tend  to  lower  the  breaking  strength; 
the  load  should  not  be  applied  too  suddenly,  as  it  may  produce 
vibration,  the  shock  from  which  often  breaks  the  briquette 
before  the  ultimate  strength  is  reached.  Care  must  be  taken 
that  the  clips  and  the  sides  of  the  briquette  be  clean  and  free 
from  grains  of  sand  or  dirt,  which  would  prevent  a  good  bearing. 
The  load  should  be  applied  at  the  rate  of  600  pounds  per  minute. 
The  average  of  the  briquettes  of  each  sample  tested  should  be 


FIG.  55. 

taken  as  the  test  excluding  any  results  which  are  manifestly 
faulty. 

Constancy  of  Volume 

Significance. — The  object  is  to  develop  those  qualities  which 
tend  to  destroy  the  strength  and  durability  of  a  cement.  As 
it  is  highly  essential  to  determine  such  qualities  at  once,  tests 
of  this  character  are  for  the  most  part  made  in  a  very  short 
time,  and  are  known,  therefore,  as  accelerated  tests.  Failure 
is  revealed  by  cracking,  checking,  swelling  or  disintegration,  or 
all  of  these  phenomena.  A  cement  which  remains  perfectly 
sound  is  said  to  be  of  constant  volume. 

Methods. — Tests  for  constancy   of  volume   are   divided  into 


82  HYDROELECTRIC  PLANTS. 

two  classes:  (1)  normal  tests,  or  those  made  in  either  air  or  water 
maintained  at  about  21°  C.  (70°  F.),  and  (2)  accelerated  tests, 
or  those  made  in  air,  steam  or  water,  at  a  temperature  of  45°  C. 
(115°  F.)  and  upward.  The  test  pieces  should  be  allowed  to 
remain  24  hours  in  moist  air  before  immersion  in  water  or  steam. 
For  these  tests,  a  pat  about  7J  centimeters  (2.95  inches)  in 
diameter,  1J  centimeters  (0.49  inches)  thick  at  the  center,  and 
tapering  to  a  thin  edge,  should  be  made,  upon  a  clean  glass 
plate  (about  10  centimeters  (3.94  inches)  square),  from  cement 
paste  of  normal  consistency. 

Normal  Test. — A  pat  is  immersed  in  water  maintained  as 
near  21°  C.  (70°  F.)  as  possible  for  28  days,  and  observed  at 
intervals;  the  pat  should  remain  firm  and  hard  and  show  no 
signs  of  cracking,  distortion  or  disintegration. 

Accelerated  Test. — (a)  A  pat  is  placed  on  a  shelf  in  a  suitable 
vessel  filled  with  fresh  water,  but  without  allowing  it  to  touch 
the  bottom.  The  water  is  then  gradually  raised  to  a  tempera- 
ture of  45°' C.  (115°  F.)  and  maintained,  at  this  temperature  for 
24  hours;  or  (b),  a  pat  is  exposed  in  any  convenient  way  in  an 
atmosphere  of  steam,  above  boiling  water,  in  a  loosely  closed 
vessel,  for  three  hours. 

To  pass  these  tests  satisfactorily  the  pats  should  remain 
firm  and  hard  and  show  no  signs  of  cracking,  distortion  or 
disintegration.  Should  the  pat  leave  the  plate,  distortion  may 
be  detected  best  with  a  straight-edge  applied  to  the  surface 
which  was  in  contact  with  the  plate.  In  the  present  state  of 
our  knowledge  it  cannot  be  said  that  cement  should  necessarily 
be  condemned  simply  for  failure  to  pass  the  accelerated  tests; 
nor  can  a  cement  be  considered  entirely  satisfactory  simply 
because  it  has  passed  these  tests. 

Submitted  on  behalf  of  the  committee:  George  S.  Webster, 
chairman;  Richard  L.  Humphrey,  secretary;  George  F.  Swain, 
Alfred  Noble,  Louis  C.  Sabin,  S.  B.  Newberry,  Clifford  Richard- 
son, W.  B.  W.  Howe,  F.  H.  Lewis. 

Simple  Tests. 

The  tests  recommended  by  the  Society  are  quite  exhaustive 
and  are  those  used  on  very  large  works  where  a  man  is  detailed 
to  the  testing  work  alone.  For  less  extensive  work,  however, 
a  more  rapid  and  less  expensive  test  is  desired. 


MATERIALS.  83 

The  following  simple  tests  can  be  made  by  the  engineer  him- 
self, with  an  outfit  costing  not  over  $4,  and  which  can  be  stored 
in  a  desk  pigeon-hole.  The  tests  thus  made  will  be  interesting 
in  themselves,  and  will  be  effective  and  convincing  aids  in  re- 
jecting most  bad  cements  which  may  be  offered,  and  will  also 
have  the  preventive  effect  of  causing  manufacturers  to  send 
their  lower  grades  of  cement  elsewhere  and  to  send  only  their 
best  products  to  the  places  where  such  tests  are  probable: 

(1)  For  Fineness. — Sift  three  to  four  ounces  of  cement  through 
a  standard  test  sieve  of  100  meshes  per  linear  inch.     Reject  ce- 
ment of  which  10  per  cent,  by  weight  is  retained  on  the  sieve. 
This  is  conservative,  and  the  limit  may  be  made  smaller,  for 
many  Portland  cements  are  now  in  the  market  which  will  leave 
less   than   four  per  cent.     A   test   by   200-mesh   sieve,   with  a 
30  per  cent,  limit,  is  desirable,  but  takes  time. 

(2)  For  Quickness  of  Setting. — Make  a  pat  of  four  ounces  of 
neat   cement,    adding   one-quarter    to    one-fifth    its    weight   of 
water  and  making  a  putty-like  ball  which  can  be  dropped  on 
the  table  and  retain  its  form  without  falling  to  pieces.     Press 
this  upon  a  3x4-inch  glass  plate,  leaving  it  ^-inch  thick  in  the 
center  and  sloping  to  thin  edges  all  around.     Note  time  required 
to  take  initial  set.     Reject  cement  which  sets  in  less  than  25 
minutes.     It  may  take  three  hours  or  more,  but  it  will  be  better 
for  paving  if  it  sets  in  one  hour.     The  instant  of  "  initial  set  " 
is  determined  by  nothing  when  the  surface  will  support  a  4-ounce 
weight  resting  upon  the  smooth  flat  end  of  a  11/12-inch  diameter 
wire. 

(3)  For  Soundness. — Use   the  pat  on   glass  above   described 
and  note  when  it  sets  enough  more  to  make  it  difficult  to  indent 
it  with  the  thumb  nail,  or  when  it  will  support  one  pound  on 
the  smooth  flat  end  of  a   1/24-inch  wire,  which  may  be  con- 
sidered as  indicating  "  a  hard  set."     Then  put  the  pat  with 
its  glass  plate  over  boiling  water  until  the  steam  has  heated 
them,  and  then  immerse  and  keep  them  in  the  boiling  water 
for   three    hours.     Reject   Portland   cement   if   the   pat   shows 
radiating   cracks   in    the    center,    or   shows   blow-holes   on   the 
surface,  or  curls  up  from  the  glass,  or  cracks  at  the  thin  edges. 
Good  natural  cements  may  fail  to  endure  this   test    (which  is 
a  severe  one) ,  and  it  may  properly  cause  the  rejection  of  some 
Portland    cements   which   would   endure   it   after   being  "  air- 
slacked  "  or  "  seasoned." 


84  HYDROELECTRIC  PLANTS. 

(4)  For  Purity. — Provide  a  glass-stoppered  bottle  of  muriatic 
acid,  two  shallow  white  bowls  or  two  J-inch  by  6-inch  test  tubes, 
a  glass  rod  and  a  pair  of  rubber  gloves.  Put  in  a  bowl  or  a  tube 
as  much  cement  as  can  be  taken  on  a  nickel  5-cent  piece;  moisten 
it  with  half  a  teaspoonful  of  water;  cover  with  clear  muriatic 
acid  poured  slowly  upon  the  cement  while  stirring  it  with  the 
glass  rod. 

Pure  Portland  cement  will  effervesce  slightly,  and  will  give  off 
some  pungent  gas  and  will  gradually  form  a  bright  yellow  jelly 
without  any  sediment. 

Powdered  limestone  or  powdered  cement-rock  mixed  with 
the  pure  cement  will  cause  a  violent  effervescence,  the  acid 
boiling  and  giving  off  strong  fumes  until  all  the  carbonate  of 
lime  has  been  consumed,  when  the  bright  yellow  jelly  will  form. 

Powdered  sand  or  quartz  or  silica  mixed  with  cement  will 
produce  no  other  effect  than  to  remain  undissolved  as  a  sedi- 
ment at  the  bottom  of  the  yellow  jelly. 

Reject  cement  which  has  either  of  these  adulterants. 

Powdered  slag  mixed  with  cement  unfits  it  for  pavement 
work.  The  adulteration  is  indicated  in  the  dry  cement  (when 
coloring  matter  does  not  conceal  it)  by  a  lilac  tint,  and  it  is 
also  indicated  on  the  surface  of  a  test-pat  after  drying  by  brown 
and  green  and  yellow  discolorations. 

A  chemical  test  will  show  the  presence  of  slag  if  made  as 
follows:  Provide  an  ounce  of  mixture  of  methylene  iodide 
(CH2I2)  and  benzine,  in  which  the  methylene  (the  specific  gravity 
of  which  is  3.292,  being  the  heaviest  organic  liquid)  is  reduced 
to  the  specific  gravity  of  2.95  by  addition  of  benzine.  The 
methylene  is  uncommon  and  costs  $1  an  ounce. 

Into  a  i-inch  test  tube  put  J-inch  of  the  dry  suspected  cement 
and  pour  in  a  little  of  the  mixture,  stirring  to  a  thin  grout 
Then  cork  the  tube  and  let  it  stand.     If  slag  is  present,  it  will 
remain  at  the  top,  while  the  cement  will  settle  to  the  bottom. 
The  separation  cannot  be  seen  if  coloring  matter  is  present. 

Coloring  matter  in  any  cement  will  show  itself  in  the  acid 
test  by  giving  a  black  or  gray  color  to  the  resultant  jelly,  which 
would  otherwise  be  yellow.  The  coloring  matter  may  or  may 
not  be  injurious  in  itself,  but  its  presence  shows  that  the  manu- 
facturer wished  to  disguise  the  cement,  which  should  be  re- 
jected, because  there  are  a  plenty  of  good  cements  which  need 
no  disguise. 


MATERIALS.  85 

Weight. — The  several  kinds  of  cement  differ  materially  in 
weight,  and  any  cement  that  varies  much  from  these  average 
weights  should  be  examined  specially. 

The  standard  barrel  contains  3.65  cubic  feet,  and  the  standard 
bag  is  one-fourth  of  a  barrel.  The  average  weight  of  a  cubic 
foot  of  packed  cement  is:  Portland,  104  to  114  pounds;  puzzolan, 
90  pounds;  natural,  75  to  82  pounds  for  Eastern  and  70  to  72 
for  Western,  the  average  net  weight  of  each  per  barrel  being 
375  pounds,  330  pounds,  300  pounds  and  265  pounds. 

Results. — These  tests  will  be  conclusive  as  far  as  they  go, 
and  will  cause  the  rejection  of  no  good  cements.  The  makers 
of  high-grade  cements  would  not  object  to  these  requirements 
and  would  not  increase  the  price  because  of  them. 

Beam  Test. 

The  best  test  of  all  is  to  construct  small  beams  of  the  actual 
materials  to  be  used  and  then  select  that  cement  and  mixture 
which  gives  the  best  results.  Of  course  tests  should  be  made 
to  determine  the  freedom  from  slag,  etc. 

For  testing  use  a  beam  2x2x24  inches.  A  heavy  timber  lever 
can  easily  be  made  for  the  center  load  test.  Then  the  formula 

P_L_       s_bd* 
4  6 

gives  the  safe  load  P.      (see  Table  XXIX) 

USES. 

During  the  process  of  manufacturing  the  cement  is  frequently 
over  or  under  burned,  making  an  inferior  quality.  This  is 
usually  mixed  in  with  the  other  cement  and  sold.  There  are 
times  when  this  inferior  cement  is  sold  to  the  small  buyer  with 
the  idea  that  it  will  not  be  tested.  It  is  to  discourage  such  acts 
that  the  cement  is  tested. 

Cement  which  has  been  over  burned  sets  with  great  rapidity 
and  there  are  times  when  the  hydraulic  engineer  wants  just 
such  cement.  By  sending  to  the  factory  such  cement  can  usu- 
ally be  procured,  and  if  wanted  in  sufficient  quantity  it  will 
be  made  especially  to  suit  the  requirements.  It  must  be  borne 
in  mind,  however,  that  such  cement  is  only  about  half  as  strong 
as  the  perfect  article. 


80  HYDROELECTRIC  PLANTS. 

By  reading  over  the  tests  for  cement,  the  virtues  desired  in  a 
good  cement  will  be  understood. 

Cement  should  be  put  up  in  barrels  though  it  adds  somewhat 
to  the  cost.  Paper  sacks  preserve  the  cement  from  loss  and 
moisture  better  than  cloth  sacks  but  are  more  liable  to  injury 
from  rough  handling.  The  most  common  form  for  shipping  is 
the  cloth  sack,  the  sacks  being  saved  and  sent  back  to  the 
factory. 

Cement  alone,  neat  cement,  is  seldom  used  unless  it  is  for 
pointing  or  plastering,  the  usual  way  being  to  mix  it  with  sand 
and  crushed  stone;  sand  and  slag;  sand  and  burnt  clay  or  gumbo, 
gravel,  cinders,  etc.  This  added  material  is  called  the  aggregate. 
The  aggregate  must  always  be  clean  and,  when  dirty,  must  be 
well  washed. 

TABLE  XXI. 

Weight  Volume  Volume 

Name.      per  bbl.  in  Ibs.  perbbl.  incu.  ft.  per  bbl.  in  cu.  ft  net. 


Portland  

380 

4 

3.6 

Natural  .  . 

300 

4 

3.6 

TABLE  XXII. 
WEIGHT  OF  CONCRETE. 

Cinder  concrete about  105  Ibs.  per  cubic  foot. 

Crushed  stone  concrete "       140 

Gravel  concrete 150 

Slag  concrete "       135 

Cement  mortar  1-2 "       116 

The  proportions  of  the  aggregate  and  cement  depend  not 
only  on  the  aggregate  but  also  on  the  character  of  the  work  for 
which  it  is  used.  Here  is  where  the  judgment  of  the  engineer 
is  brought  into  play. 

The  walls  for  flumes,  penstocks,  canal  lining,  floors,  etc., 
should  be  in  the  proportion  of  1J  barrels  Portland  cement 
to  the  cubic  yard  of  gravel  having  the  proper  proportion  of 
sand  and  gravel,  or  if  crushed  stone  is  used,  the  proportion, 
one  cement,  two  sand  and  four  stone  is  good  practice.  For  less 
important  work  one  barrel  of  cement  to  the  cubic  yard  of  gravel 
and  1-3-6  if  stone  is  used. 


MATERIALS.  87 

The  amount  of  water  used  in  mixing  is  one  of  the  open  ques- 
tions. The  best  engineering  practice,  however,  outside  of  the 
laboratories,  seems  to  be  to  use  enough  water  so  that  when  the 
concrete  is  tamped  into  the  forms  water  stands  on  the  surface 
and  the  whole  mass  quakes  when  tamped. 

A  wet  concrete  is  more  apt  to  be  well  made  than  a  more  dry 

TABLE  XXIII. 
CONCRETE  AGGREGATES. 

Cement.  Sand.  Gravel.    Crushed  Character  of  Work. 

Stone. 


1 

6 

Culvert  sides  and  bottom. 

1 

5 

Culvert  arch. 

1 

4 

Culvert  arch  especially  strong. 

1 

1 

Water-tight  under  high  pres- 

sure. 

1 

2  or  2J 

4 

Water-tight  under  high  pres- 

sure equally  good. 

1 

2J 

5 

Penstocks,  lining  for  reser- 

voirs. 

1 

3 

6 

Generator  and  building  foun- 

dations. 

1 

2 

3 

Lining  for  reservoirs. 

1 

3 

6 

Backing  for  reservoirs. 

1 

3 

5 

Piers  and  abutments. 

1 

7 

Steel  concrete  bridges  25  foot 

to  35  foot  span. 

1 

2 

4 

Steel  concrete  bridges  arches 

span  40  feet  to  60  feet. 

1 

6 

Sewers. 

1 

7 

Large  breakwater. 

1 

3 

Steel    concrete    piling,    5000- 

pound  hammer. 

1 

2J 

5 

Floor  slabs. 

1 

2 

4 

Beams. 

mixture.  Special  work  which  is  under  the  eye  of  the  engineer 
can  be  done  with  the  minimum  amount.  Numerous  experi- 
ments have  proven  that  a  wet  concrete  gets  practically  as  strong 
as  the  more  dry  mixture. 

In  Table  XXIII  are  given  some  of  the  mixtures  used  on  im- 
portant works,  actually  built,  in  the  United  States. 


88  HYDROELECTRIC  PLANTS. 

SAND    CEMENT. 

In  the  West,  when,  owing  to  high  freight  rates  and  difficulties 
of  transportation,  the  price  of  cement  reaches  a  high  figure,  the 
conditions  are  such  that  sand  cement  demands  recognition. 

F.  L.  Smidth  is  the  inventor  and  a  royalty  of  10  cents  per 
barrel  is  charged. 

The  silica  sand  is  placed  in  a  revolving  drum  in  which  are 
pebbles  of  great  hardness.  These  pebbles  grind  the  sand  and 
equal  volume  of  cement  up  into  a  much  finer  dust  than  was  even 
the  cement  before  it  was  put  in.  The  combined  mixture  of  half 
sand  and  half  cement  is  then  assumed  as  being  all  cement,  and 
used  with  the  usual  proportions  of  gravel  or  sand  and  stone. 

Experience  with  it  in  California  indicates  that  it  gives  good 
results. 

The  following  is  the  itemized  cost  of  a  barrel  of  sand  cement, 
given  in  Water  Supply  and  Irrigation: 

One-half  barrel  Portland  cement $5 . 00 

One-half  barrel  sand .18 

Grinding  sand .20 

Royalty 05 


Total  cost  of  375  pounds  sand  cement $5 . 43 

The  above  was  ground  so  that  95  per  cent,  passed  a  180-mesh 
sieve. 

Using  340  pounds  of  the  above  per  cubic  yard  of  concrete  we 
have  the  following  cost  per  cubic  yard  of  concrete: 

Cement  sand $4.93 

Sand 50 

Crushed  rock  and  gravel 2 . 50 

Labor .  .  1 . 00 


Total $8. 93 

BURNT    CLAY    AND    GUMBO. 

The  engineer  is  often  called  upon  to  do  concreting  where  there 
is  no  stone  or  gravel.  In  such  localities  there  is  usually  clay 
or  gumbo  which  may  be  burned  and  used  in  the  place  of  the 
broken  stone.  The  clay  or  gumbo  is  burnt  as  follows:  Cord 
wood  is  piled  in  a  pile,  say  12x12x1  foot.  On  this  spread 
a  layer  of  coal  or  slack  about  four  inches  thick,  and  on  top  of  all 
15  to  20  inches  of  clay  or  gumbo. 


MATERIALS. 


89 


On  firing  the  wood  enough  air  enters  the  pile  to  enable  slow 
combustion  without  vitrifying  the  material.  This  process  costs 
from  25  to  40  cents  per  cubic  yard.  Shrinkage  of  these  clays  is 
about  12  per  cent,  during  burning,  and  the  crushing  strength 
of  the  burnt  product  is  often  as  high  as  400  pounds  per  square 
inch. 

Gumbo  is  a  black,  sticky  mud,  found  along  most  of  the  rivers 
of  the  United  States,  especially  in  the  Central  and  Western 
States.  It  is  now  being  used  to  quite  an  extent  for  railroad 
ballast  and  highways. 

Table  XXIV  shows  how  the  various  items  of  expense  are  dis- 
tributed. Of  course,  the  items  of  labor,  forms,  mixing  and 
placing,  will  vary  with  every  case.  The  costs  are  given  in 
dollars  per  cubic  yard. 

TABLE  xxrv. 

COST  IN  DOLLARS  OF  CONCRETE  WORK  PER  CUBIC  YARD. 


Character  of  the  Work. 

Labor  and 
General 
Expenses. 

Forms. 

Lumber 
in 
Forms. 

Mixing 
and 
Placing. 

Power  house   walls.      Surface  finished  in 
rock  work  

.20  to  .30 

.60  to  .75 

.40  to  .60 

1.  to  1.5 

Power  house  walls.     Surface  rough  

.20  to  .25 

.50  to  .60 

.35  to  .50 

1  .  to  1  .25 

Foundations  for  buildings,  generators,  etc. 

.15  to  .20 

.15  to  .25 

.10  to  .12 

.8  to  1  00 

Canal  slopes  and  bottoms  (filling)  
Canal  slopes  and  bottoms  (surface) 

.10  to  .20 
12  to  25 

.10  to  .15 
25  to  35 

.01  to  .05 
01  to  10 

.8  to  1  25 
1  25  to  1  5 

Walls    having    numerous    windows,    etc. 
Fancy  work  

.25  to  .40 

1  .50  to  2.0 

.75  to  1  .00 

1.5  to  1  75 

COSTS. 

A  few  years  ago  the  idea  obtained  that  concrete  should  cost 
at  least  $6  per  yard,  but  experience  has  robbed  concrete  of  all 
its  mystery  and  we  must  accept  it  as  the  best  friend  the  engineer 
has  to-day. 

In  1903  the  author  built  a  large  power-house,  the  concrete 
for  which  cost  as  follows: 


Hand  Mixed 


All  labor  (hand-mixing).. 

Gravel 

Labor  on  forms 

Cement,  li  barrels. . .    


$0.75  per  cubic  yard 

25"       "         " 
.68   '       "          " 
2.52   '       " 


Total $4.20  " 


90  HYDROELECTRIC  PLANTS. 

The  forms  were  built  of  the  plank  and  timber  used  in  the 
construction  of  the  dam  and  so  cost  nothing.  The  outside  of 
the  power-house  was  finished  to  represent  coursed  masonry. 
The  concrete  was  all  hand-mixed,  the  gravel  being  dumped 
from  wagons  holding  just  one  cubic  yard,  directly  upon  the 
mixing  platform.  This  cost  is  for  the  concrete  tamped  in  place, 
and  allows  for  all  shrinkage  from  the  batch  measurements. 

HAND-MIXED   CONCRETE. 

In  mixing  by  hand  or  machine  the  crushed  stone  should  be 
well  washed  off  by  means  of  a  stream  of  water  as  it  comes  on  to 
the  platform.  If  wheel-barrows  are  used  they  should  be  of  steel 
and  have  numerous  holes  drilled  through  the  bottom  to  allow 
the  water  to  drip  off.  The  cement  should  not  be  taken  from 
the  sack  to  measure,  simply  allow  9/10  cubic  feet  per  sack  of 

TABLE  XXV. 

SIZES  OF  GAUGE  BOXES. 


Proportions. 

/  Sand    Box.  — 
Size. 

Vol. 
cu.ft. 

,  Stone 
Size. 

Box.  x 

Vol. 
cu.ft. 

1—  2J—  4 

2'9"X2'  XI  '8" 

9.25 

5'X4'  5F 

14.80 

1—3  —6 

2'  9"  X2'  X2'  0" 

11.10 

5'X6'8" 

22.20 

1—2  —5 

2'9*X2'X1'  4" 

7.40 

5'X6'  6i* 

18.50 

i_2J—  6J 

2'9"X2'X1'8" 

9.25 

*    5'  X7'  2Y 

24.05 

95  to  100  pounds.  If  gravel  is  used  it  should  not  be  washed 
unless  the  gravel  has  more  than  10  per  cent,  by  weight  of  loam 
or  15  per  cent,  of  clay,  as  it  has  been  found  that  up  to  these  pro- 
portions the  strength  is  improved  by  the  loam  or  clay. 

When  the  mixing  is  in  a  cramped-up  place  where  wheel- 
barrows have  to  be  used  and  the  foreman  is  of  the  second  class, 
the  JDest  plan  is  to  have  the  wheel-barrows  dumped  into  gauge 
boxes.  Table  XXV  gives  the  sizes  of  some  gauge  boxes  found 
convenient  for  the  proportions  given.  The  sand  box  is  placed 
on  the  platform  and  filled  level  full.  The  desired  amount  of 
cement  is  then  mixed  with  the  sand,  the  box  having  been  re- 
moved, and  alongside  the  sand  cement  the  stone  box  is  filled 
with  the  washed  stone,  the  box  removed  and  the  cement  sand 
mixed  with  it  once  over,  the  necessary  water  being  played  on  it 
through  a  garden  sprinkler. 


MATERIALS.  91 

The  more  the  concrete  is  mixed  the  better,  but  the  above 
mixing  ensures  good  work. 

For  arch  construction  use  fine  crushed  stone  or  gravel,  of  an 
even  size,  not  to  exceed  one-inch  grade.  To  determine  the 
exact  mixture,  take  a  vessel  full  of  stone  or  gravel  and  fill  the 
space  in  same  with  sand,  by  shaking  the  sand  into  the  stone 
until  the  bulk  begins  to  enlarge,  showing  that  no  interstices 
remain  unfilled,  then  measure  the  proportions  of  sand  and  stone. 
Use  one  portion  of  Portland  cement  to  three  portions  of  sand,  and 
proportion  of  crushed  rock  as  the  test  may  determine. 

Beams  are  always  tension,  and  the  floor  above  acts  as  the 
compression  member,  consequently  the  highest  quality  of  ten- 
sion concrete  is  required,  which  is  gravel  or  fine  crushed  stone  of 
not  over  one-half-inch  grade. 

Cinders  are  not  as  valuable  for  beam  as  for  floor  or  arch  con- 
struction, where  their  lightness  is  a  consideration. 

Under  ordinary  conditions,  unless  exposed  to  excessive 
heat  or  excessive  rain,  the  following  is  a  safe  table  for  the 
strength  of  concrete: 

TABLE  XXVI. 

When    30  days  old    60  per  cent,  of  full  strength 

60    "       "       75 

90  "  "  85 
"  120  '  "  CO 
"  180  "  "  95 
"  360  "  "  ICO 

The  extent  to  which  concrete  is  hurt  by  freezing  can  be  ascer- 
tained by  estimating  that  after  freezing  it  will  not  develop  more 
than  40  per  cent,  of  the  balance  of  the  strength  it  would  have 
attained  had  it  not  frozen. 

The  most  economical  and  expeditious  method  for  hand  mixing 
is  to  dump  the  gravel  or  sand  and  stone  directly  from  the  wagons 
holding  one  cubic  yard  on  to  a  large  mixing  board  having  an 
area  of  about  24x32  feet. 

If  stone  and  sand  are  used  for  the  aggregate,  two  wagon  loads 
of  stone  are  dumped,  making  two  piles  in  line  on  the  board. 
A  wagon  having  a  fixed  partition  extending  down  the  middle 
of  the  wagon  box,  and  loaded  so  that  one-half  of  the  load  of 


92 


HYDROELECTRIC  PLANTS. 


sand  is  just  right  for  the  cubic  yard  of  stone,  is  then  driven  over 
the  stone  piles  and  a  half  dumped  on  top  of  each  pile.  Four 
men  with  square  pointed  shovels  (two  at  each  end  of  the  pile) 
then  commence  at  the  ends  and  turn  the  sand  and  stone  over, 
working  toward  the  middle.  When  it  is  all  turned  over  the 
board  men  turn  around  and  work  the  pile  back  into  its  former 
position.  The  cement  is  now  scattered  over  the  top  of  the  pile 
by  the  man  who  usually  acts  as  a  sub  foreman.  The  board  men 
then  repeat  the  first  mixing  operation,  water  being  sprinkled 
on  the  mixture  in  the  meanwhile,  through  a  garden  sprinkler. 
Wheelbarrows  take  the  concrete  away,  having  been  filled  by 
the  board  men.  The  board  men  should  be  the  pick  of  the  work- 
men and  should  receive  10  per  cent,  more  pay.  Three  batches 


FIG.  56 

should  be  run  all  the  time  in  order  to  get  the  most  efficient 
results,  and  all  the  men  should  be  employed  necessary  to  take 
care  of  every  detail  of  the  work.  It  is  very  poor  policy  to  skimp 
the  help  in  concrete  mixing. 

An  ordinary  No.  4  tank  pump,  worked  by  two  men,  will  raise 
enough  water  20  or  30  feet  to  wet  100  cubic  yards  of  concrete 
per  day. 

If  the  concrete  is  made  of  sand  gravel  the  first  mixing  is,  of 
course,  unnecessary,  and  the  cement  is  spread  directly  over  it 
and  mixed  twice  over  by  the  four  board  men. 

MACHINE    MIXED    CONCRETE. 

On  large  work  it  becomes  necessary  to  handle  the  concrete 
in  such  bulk  that  hand  mixing  becomes  too  slow  and  expensive. 


MATERIALS 


93 


For  a  small  job  the  cost  of  transporting  and  setting  up  a  mixer 
makes  the  cost  more  than  if  done  by  hand,  but  when  thousands 
of  cubic  yards  are  made  the  machine  mixed  concrete  is  much 
cheaper.  There  are  many  forms  of  mixers  on  the  market, 
though  all  may  be  divided  into  two  classes,  gravity  and  mechan- 
ical. The  gravity  mixer  (see  Fig.  56)  depends  on  the  force  of 
gravity  to  mix  the  aggregate  as  it  falls  down  a  spout  lined 


FIG.  57. — Concrete  plant. 

with  projections  which  deflect  the  concrete  from  side  to  side, 
and  thus  mix  it.  These  mixers  are  quite  cheap  and  simple, 
but  there  is  reason  to  believe  that  they  do  not  give  as  good 
results  as  do  the  mechanical  mixers,  though  they  compare 
favorably  with  the  usual  hand  mixed  cement.  Of  the  mechan- 
ical mixers  the  cubical  mixer  is  one  of  the  best.  It  consists 
simply  of  a  square  metal  box  mounted  on  an  axis  passing 
through  two  opposite  corners  and  revolved  by  steam,  electric; 


94  HYDROELECTRIC  PLANTS. 

gasoline  or  other  power.  The  proper  amount  of  water  is  fed 
into  the  box  through  a  pipe  and  the  batch  is  dumped  in  through 
a  door.  Where  the  work  to  be  done  is  extensive  it  will  pay  to 
fix  up  a  good  concrete  plant.  In  Fig.  57  is  shown  an  elevation 
view  of  a  mixing  plant.  A  large  bin  is  provided  for  the  stone 
and  sand.  Under  the  bin  is  a  measuring  box  having  a  movable 
partition  so  that  any  proportion  of  sand  and  stone  can  be 
obtained.  The  cement  is  dumped  into  a  sheet  iron  chute 
which  empties  into  the  measuring  box.  The  measuring  box 
dumps  into  the  mixer  through  a  canvas  tube.  The  mixer  is 
placed  high  enough  above  the  ground  so  that  cars  or  one  horse 
carts  may  pass  under  for  filling. 

All  mixers  into  which  a  certain  amount  of  aggregate  is  dumped, 
mixed  and  drawn  off  after  the  motion  of  the  machine  has  stopped, 
are  called  batch  mixers.  That  is  a  batch  is  mixed  and  emptied 
and  then  another  is  put  in. 

To  avoid  the  delay  of  waiting  to  fill  and  dump,  continuous 
mixers  are  sometimes  used.  In  these  mixers  the  proper  aggre- 
gates are  fed  in  at  one  end  of  the  mixer  continuously,  and 
taken  out  at  the  other  end. 

It  is  generally  conceded  that  machine  mixed  concrete  is  the 
best.  The  cost  of  mixing  concrete  by  machine  is  from  50  to 
70  cents  per  cubic  yard.  This  includes  all  machine  expense  and 
placing  the  concrete  in  the  forms,  but  does  not  include  the 
forms,  tamping  or  cost  of  material. 

FORMS. 

Next  in  importance  to  the  mixture  of  the  concrete  is  the 
building  of  the  forms.  It  requires  the  constant  vigilance  of 
the  engineer  to  produce  good  results  with  the  class  of  labor 
usually  to  be  procured.  The  forms  must  be  so  built  that 
there  will  be  no  springing  of  the  plank.  When  the  work  is 
rushed  the  green  concrete  may  be  several  feet  deep  in  the 
forms  and  the  top  being  constantly  tamped,  causes  great  pres- 
sure on  the  sides.  If,  after  the  concrete  has  partly  set,  the 
forms  spring  ever  so  little,  the  concrete  assumes  a  new  position 
and  a  large  part  of  its  strength  is  gone. 

On  large  engineering  jobs  there  is  usually  a  great  amount  of 
rough  lumber  used  in  which  case  the  forms  may  be  built  of  it, 
using  the  heavy  timber  for  posts  and  the  two-inch  plank  surfaced 


MATERIALS. 


95 


on  one  side  and  edged  for  the  sheeting.  It  must  be  remembered 
that  the  concrete  will  reproduce  the  finest  cracks  and  grain 
in  the  wood  sheeting,  so  great  care  must  be  taken  to  have  the 
surface  perfectly  smooth  and  level.  The  forms  should  be  washed 
with  soft  soap  just  before  filling  and  any  cracks  or  rough  places 
should  be  filled  with  hard  soap,  putty,  or  any  other  filling 
which  will  not  discolor  the  concrete.  Opposite  posts  should  be 
tied  together  by  means  of  soft  iron  wire  passed  through  several 
times,  then  twisted  up  tightly.  This  is  the  safest  and  cheapest 
method  of  stiffening.  One-half  inch  bolts  may  be  used  but 
they  cost  more  and  are  more  difficult  to  obliterate  from  the 
exposed  surface  of  the  finished  concrete. 

Arches  are  formed  over  centers  something  like  that  shown 


FIG.  58. 

in  Fig.  58.  No  part  of  the  form  work  should  be  more  rigid  than 
the  centers.  Plenty  of  bracing  should  be  used  especially  when 
the  timbers  can  afterwards  be  used  on  the  works  so  that  their 
only  cost  is  the  putting  in  place.  The  center  above  the  spring- 
ing line  A  B,  is  built  in  any  convenient  place  and  then  carried 
out  and  stood  upon  the  posts.  The  ribs  should  not  be  more 
than  two  feet  apart. 

Great  care  must  be  taken  not  to  remove  the  forms  too  soon. 
A  common  rule  is  to  allow  them  to  stand  nine  days,  but  while  this 
is  longer  than  necessary  for  some  work,  it  is  not  enough  for 
other.  A  long  arch  should  stand  two  or  three  weeks,  while 
thin  walls  only  meant  to  maintain  a  vertical  pressure,  can  be 
uncovered  in  three  or  four  days  if  necessary. 


96 


HYDROELECTRIC  PLANTS. 


ROCK    WORK. 


Plain  concrete  looks  too  much  like  plaster  to  present  a  good 
appearance,  so  the  surface  is  usually  made  to  resemble  rock 
work  by  tacking  strips  to  the  sheeting  as  in  Fig.  59.  The 
appearance  thus  procured  will  add  from  three  to  four  cents 
per  square  foot  to  the  cost  of  the  form  but  will  be  worth  much 
more  than  that  where  a  fine  appearance  is  desired. 

Arches  may  be  given  the  proper  appearance  as  shown  in  Fig. 
60.  The  strips  used  to  form  this  rock  work  are  surfaced  all 


FIG.  59. 

over  and  must  be  of  clear  stuff,  the  size  may  be  made  to  suit 
the  taste,  but  the  section  given  in  the  lower  part  of  Fig.  60 
gives  good  results. 

SURFACING. 

Where  a  fine  appearance  is  desired  the  following  method  of 
surfacing  is  used:  As  soon  as  the  forms  are  removed  and  while 
the  concrete  is  somewhat  soft,  the  surface  is  rubbed  with  pieces 
of  grindstone  or  blocks  of  concrete  having  handles  moulded  in 
and  composed  of  one  part  cement  to  two  parts  sand.  The  sur- 


MATERIALS. 


97 


face  is  then  wet  down;  washed  with  a  coat  of  grout,  of  one  part 
cement  to  one  part  sifted  sand,  and  rubbed  with  a  wooden 
float.  This  finish  will  not  peel  and  is  hard  and  of  uniform 
color.  The  concrete  may  be  pricked  or  tooled  to  make  it  more 
nearly  resemble  real  rock. 


FIG.  60. 


Use  sheets  of  steel,  called  facing  boards,  for  the  purpose  of 
holding  the  coarse  concrete  away  from  the  surface  which  it  is 
desired  to  finish,  and  have  thin  grout  of  one  part  cement  to 
two  parts  sand  filled  in  between  the  facing  boards  and  the 
form  as  shown  in  Fig.  61. 


"  .   * 


FIG.  61. 

When  strips  are  used  to  get  the  rock- work  effect,  the  facing 
board  is  merely  a  sheet  of  iron  or  steel  with  holes  in  the  top 
corners  to  admit  of  their  being  lifted.  But  when  the  surface 
is  plain  the  facing  boards  have  ribs  attached  as  in  Fig.  62  to 
keep  them  an  inch  or  so  away  from  the  form. 


98 


HYDROELECTRIC  PLANTS. 


The  size  of  the  boards  will  depend  on  the  size  of  the  walls 
and  usually  several  lengths  are  used.  The  width  should  be 
about  12  inches. 

A  coal  scuttle  having  a  straight  edged  snout  is  handy  for 
pouring  the  grout  in  between  the  boards  and  the  form. 

Where  possible,  build  the  forms  up  to  full  height  at  the  start 


FIG.  62. 

and  dump  the  concrete  at  all  stages  of  the  work  from  the  top 
level.  In  hydraulic  work  this  can  usually  be  done  as  the  em- 
bankments have  to  be  built  to  the  top  levels  and  the  mixing 
boards  may  be  placed  on  the  embankment.  The  necessary 
shoveling  of  the  concrete  back  into  place  counteracts  the  ten- 
dency of  the  concrete  to  unmix  in  falling 


FIG.  63. 


CONCRETE   LAID   UNDER   WATER. 

Concrete  properly  laid  under  water  will  have  a  greater  strength 
than  if  laid  in  the  air.  All  currents  must  be  avoided,  and  if 
this  is  impossible,  the  mixture  must  be  enough  richer  in  cement 
to  allow  for  that  washed  out.  There  are  several  methods  for 
depositing  concrete  under  the  water,  the  best  of  which  is  shown 
in  Fig.  63.  A  large  square,  steel  or  wood  bucket  is  made  having 
trap  doors  as  shown.  By  pulling  the  wire  A  the  bottom  is  let 


MATERIALS. 


99 


down  and  the  concrete  deposited.  The  box  may  hold  as  much 
as  a  cubic  yard  or  more  of  concrete  and  is  handled  by  means 
of  a  derrick.  A  tube  as  in  Fig.  64  is  often  used  on  small  work 
or  even  a  canvas  bag,  the  idea  being  to  get  the  concrete  on  to 
the  bottom  without  washing  out  the  cement.  Concrete  simply 
dumped  into  the  water,  unless  it  is  very  rich  and  the  water 
shallow,  is  worthless. 

When  the  current  cannot  be  stopped  concrete  may  be  depos- 
ited in  sacks  partly  filled  and  tamped  with  a  heavy  tamp.  A 
large  piece  of  canvas  held  against  the  current  and  the  concrete 
deposited  against  it  often  keeps  one  out  of  a  serious  difficulty. 

GENERAL  REMARKS. 

In  depositing  the  layers  of  concrete  in  the  forms  it  is  neces- 
sary to  keep  the  courses  level,  otherwise  the  facing  boards 


FIG.  65. 

cannot  be  successfully  used  and  the  exterior  finish  will  show 
scars.  Courses  should  be  run  clear  across  arches  as  in  Fig.  65. 
Concrete  begins  to  set  the  moment  it  is  wet  and  the  quicker  it 
is  placed  in  the  form,  and  the  less  it  is  disturbed  when  so  placed, 
the  stronger  will  it  be.  Thus,  if  the  forms  spring  after  a  few 
hours  of  setting  the  strength  is  greatly  impaired.  No  blasting 
should 'be  done  near  the  concrete  till  it  has  set  for  at  least  two| 
to  five  days. 

Before  each  course  is  laid  the  preceding  layer  must  be  thor- 
oughly swept  off  and  wet  down.  All  surfaces  between  layers 
must  be  left  as  rough  as  possible,  and  where  a  first  class  job  is 
desired  these  partly  dried  surfaces  after  being  wet  down  should 
be  coated  with  a  thin  layer  of  grout  of  one  part  cement  and  two 
parts  sand.  This  greatly  increases  the  strength  of  the  joint. 


100  HYDROELECTRIC  PLANTS. 

If  concrete  is  deposited  and  left  exposed  to  the  sun,  the 
result  will  be  that  at  least  one-half  an  inch  of  the  top  surface 
will  be  absolutely  dead  and  will  form  a  serious  parting  line  in 
the  wall,  as  the  next  layer  will  not  adhere  to  it.  Keep  the 
surfaces  wet,  covered  with  a  damp  canvas,  straw,  etc. 

The  edges  of  the  coping  may  be  rounded  with  a  Crafts  edger 
or  with  a  wood  fillet  and  the  joints  struck  with  a  Crafts  jointer. 

PECULIARITIES  OF  CONCRETE. 

Concrete  expands  from  heat  and  about  the  same  amount 
from  absorption  of  moisture. 

The  deck  of  a  reinforced  concrete  dam  will  expand  about 
-J-inch  per  100  feet  when  the  water  is  raised  upon  it. 

An  iron  rod  embedded  in  the  concrete  is  gripped  firmly  by 
the  contraction  and  the  average  resistance  to  pulling  out  is 
about  500  pounds  per  square  inch  of  surface. 

Anchor  bolts  grouted  in  with  neat  cement  will  resist  ex- 
tracting better  than  if  set  in  lead  or  sulphur. 

The  sun  shining  on  a  concrete  pier  tends  to  warp  it. 

Slag  cements  have  not  yet  been  proved  reliable  for  hydraulic 
work. 

Natural  cements  should  never  be  used,  especially  where  ex- 
posed to  frost. 

Concrete  has  no  safe  tensile  strength. 

Concrete  allowed  to  set  in  a  pipe  contracts  so  that  it  may 
be  shaken  out. 

Good  concrete  contracts  or  expands  for  each  degree 

^uu,uuu 

Fahrenheit  change  in  temperature. 

A  concrete  strut  placed  between  two  unyielding  abutments 
will  set  up  a  pressure  within  itself  of  15  pounds  per  square 
inch  for  each  change  of  one  degree  Fahrenheit  temperature. 

CONCRETE  IN  FREEZING  WEATHER. 

It  frequently  becomes  necessary  to  lay  concrete  in  freezing 
weather.  If  the  concrete  freezes  its  strength  is  less  than  half 
what  it  would  otherwise  be.  To  prevent  freezing  the  water 
used  is  made  quite  salt.  Barrels  half  full  of  salt  are  kept  full 
of  hot  water  and  frequently  stirred  up.  All  the  water  used  is 
taken  from  them.  The  concrete  is  then  rushed  into  the  forms 


MATERIALS.  101 

and  covered  with  a  canvas  and  a  layer  of  manure  or  compact 
straw  or  hay.  If  deposited  in  water,  the  water  keeps  out  all 
frost.  If  freezing  cannot  be  prevented  use  plenty  of  cement 
and  salt.  Salt  does  not  affect  the  strength  of  the  concrete. 

Concrete  so  made  sets  very  slowly  and  is  dangerous  where  it 
is  to  sustain  pressure  in  less  than  two  or  .three  months  time. 
Large  fires  built  on  the  windward  side  will  keep  the  tem- 
perature below  freezing.  Often  a  large  tent  may  be  placed 
over  the  work  during  construction,  and  heated  by  means  of 
large  piles  of  cordwood  kept  burning  constantly. 

A  tent  150  feet  long  and  60  feet  wide  can  be  bought  for  from 
$500  to  $600. 

Concrete  must  not  be  placed  on  frosty  steel  reinforcing  as 
the  concrete  drops  away  on  the  under  side  when  forms  are 
removed. 

TABLE  XXVII. 
EFFECT  OF  AGE  AND  FROST  IN  STRENGTH  OF  CONCRETE. 


Age. 
days. 

Strength 
pounds  per  square  inch. 

Remarks. 

9 

213 

Tested  in  usual  way. 

28 

275 

Tested  in  usual  way. 

7 

123 

Tested  in  dry  room. 

28 

130 

Tested  in  dry  room. 

7 

80 

(  Frozen  every  night  and 

28 

100 

(  thawed  every  day. 

7 

88 

Frozen  all  the  time. 

28 

108 

Frozen  all  the  time. 

There  is  no  absolute  necessity  of  using  salt.  Shelters  should 
be  placed  over  mixer  and  stoves  placed  inside  the  structures. 

Hot  water  should  be  used  and  the  sand  heated. 

As  far  as  could  be  determined  without  actual  tests,  the  salt 
does  not  retard  setting,  as  where  the  concrete  was  kept  heated 
it  set  quickly. 

After  the  concrete  has  been  deposited  it  should  be  immedi- 
ately covered  with  tar  paper  and  over  the  paper  should  be 
spread  about  10  inches  of  manure. 

As  long  as  the  interior  of  the  structures  is  kept  heated  the 
concrete  on  the  exterior  and  next  to  the  forms  will  not  freeze. 


102  HYDROELECTRIC  PLANTS 

The  concrete  under  the  tar  paper  will  not  freeze  and  will  get 
very  hard. 

Exposed  concrete  which  can  not  be  heated  from  within 
can  be  encased  with  manure  outside  the  forms. 

It  has  been  found  convenient  to  provide  a  trap  door  in  the 
outside  lagging  so  that  the  setting  of  the  concrete  could  be 
watched. 

Some  authorities  claim  that  Improved  Union  cement  is  the 
best  to  use  in  cold  weather.  One  rule  is  that  slow  setting 
Portland  must  not  freeze  in  less  than  four  days  after  placing, 
and  quick  setting  can  freeze  in  12  hours  if  kept  frozen  till  set. 

Some  interesting  experiments  were  recently  made  on  slag 
cement  (not  slag  Portland)  with  the  results  shown  in  Table 
XXVII. 

CONCRETE-STEEL. 

Concrete  possesses  the  qualities  of  permanence  and  great 
crushing  strength  but  little  or  no  tensile  or  shearing  strength. 
It  is  the  purpose  of  steel  reinforcing  to  give  to  the  concrete  these 
two  items  of  strength  which  it  lacks.  The  ideal  reinforcing  is 
such  as  to  form  a  beam  which  will  always  fail  at  the  center  by 
pulling  apart  the  steel  bars,  and  at  no  other  part.  When  con- 
crete fails  by  shearing  it  fails  between  wide  limits  and  a  large 
factor  of  safety  is  necessary,  but  when  all  the  tension  is  carried 
by  the  reinforcing,  the  factor  of  safety  need  be  only  such  as  is 
used  for  steel  work. 

Scientific  reinforcing  does  not  teach  the  filling  up  of  the 
concrete  with  large  steel  beams  as  is  sometimes  done,  but  to 
distribute  the  proper  amount  of  comparatively  small  rods 
throughout  the  mass  and  in  such  a  way  as  to  take  up  all  ten- 
sional  moments.  Steel  expands  .0000064  part  of  its  length  for 
each  degree  Fahrenheit,  while  concrete  expands  about  .0000057 
of  its  length  for  each  increase  of  one  degree  Fahrenheit.  This 
means  that  in  the  case  of  a  steel  beam  20  feet  long  imbedded 
in  concrete,  there  will  be  a  difference  in  the  expansion  and  con- 
traction from  maximum  to  minimum  temperatures,  of  about 
1/16  inch,  Though  this  is  a  small  amount,  it  is  enough  where 
the  reinforcing  is  large  beams,  to  destroy  all  adhesion  between 

the  steel  and  concrete.    Concrete  shrinks  on  setting  about         . 

1UUU 

part  of  its  dimensions.     Therefore,  if  there  is  a  large  I-beam 


MATERIALS. 


103 


imbedded  in  its  mass  as  in  Fig.  66  there  is  a  tendency  to  form 
a  crack  as  shown.  The  crack  does  not  necessarily  occur,  but  a 
strain  is  set  up  which  weakens  the  wall.  For  these  reasons 


FIG.  66. 

large  steel  beams  should  not  be  used  for  reinforcing,  but  some 
of  the  many  patent  reinforcing  bars  made  especially  for  the 
purpose.  The  Ransom  bar  is  one  of  the  best  known  and  con- 
sists of  a  square  bar,  say  one  inch  square  twisted  many  times. 


FIG.  67. 


FIG.  68. 

The  International  Fence  and  Fireproofing  Company  of  Comm- 
bus,  O.,  make  a  stranded  cable  which  is  used  in  connection  with 
woven  wires  as  in  Figs.  67-68. 


104 


HYDROELECTRIC  PLANTS. 


The  Trussed  Concrete  Steel  Company  of  Detroit,  Mich.,  have 
perfected  a  system  of  reinforcing  which  is  undoubtedly  one  of 
the  best  we  have,  They  have  conducted  numerous  tests  o. 
beams  and  slabs  which  should  be  of  great  value  to  the  engineer. 
It  will  be  seen  that  the  heavier  beams  are  about  half  as  strong 
as  steel  beams  of  the  same  depth. 

Figs.  69-72  show  a  few  of  the  uses  for  the  reinforcement. 
Fig.  73  shows  the  bar. 

The  cost  of  the  International  cables  is  about  2J  cents  per  foot, 
and  their  metallic  sheeting  costs  3  cents  per  square  foot.  The 


FIG.  69. 

Kahn  bars  cost  about  3.9  cents  per  pound  for  the  small  bars,  and 
3.25  cents  for  the  larger. 

In  Fig.  74  is  shown  a  type  of  hollow  concrete  steel  construction 
(Ransom)  which  possesses  many  valuable  features.  Any  form 
of  reinforcing  may  be  used.  The  cost  is  about  25  to  35  cents 
per  square  foot  of  exterior  surface. 

Fig.  75  shows  one  method  of  forming  the  air  cells  a,  a',  etc. 
The  corner  curve  posts  B  are  covered  on  the  sides  c,  c',  with  sheet 
iron  and  are  not  fastened  to  the  rest  of  the  form.  The  two  parts 
D,  D'  are  separate  from  the  posts.  The  brace  E  is  a  piece  of 
2x6-inch  timber,  and  two  are  used  to  hold  each  form  in  place. 


MATERIALS. 


105 


The  forms  are  about  four  feet  high.  The  brace  is  removed  first 
and  the  posts  pulled  out  when  the  entire  form  easily  comes  out. 
The  posts  are  allowed  to  project  enough  above  the  form  to  permit 
a  chain  being  attached  for  pulling  them  out. 

At  Charles  City,  la.,  the  writer  has  just  completed  a  re- 
inforced concrete  penstock,  1100  feet  long  and  having  a  capacity 
of  18,000  cubic  feet  per  minute.  The  loss  of  head  will  be  12 
inches. 


2.C 


1 

J 

.4-4-4- 

-r-T-i- 

-1—  t- 

—  rr 

±"IJ! 

1-i-t- 

1 

-4-,-L-i 

—  14~ 

-4-4-4-j 

1      1 

!      !      i      ' 

;     ;     | 

> 

\                             , 

FIG.  70. 

Fig.  76  shows  how  the  forms  were  constructed.  The  lagging 
was  -J  inch  flooring,  3  inch  being  used  on  the  curves.  The 
sections  were  12  feet  long  and  had  five  ribs  per  section.  Fifteen 
sections  were  built  which  made  182  feet  of  penstock.  The  outer 
forms  were  made  of  2  inch  surfaced  plank  and  6  by  8  inch  posts, 
on  4  foot  centers. 


106 


HYDROELECTRIC  PLANTS. 


As  the  work  progressed  many  improvements  were  made  in 
the  inner  forms  and  these  are  shown  in  the  figures. 

It  was  found  to  be  very  difficult  to  clean  the  bottom  at  d, 
and  the  bottom  forms,  e,  were  made  so  that  they  could  be  moved 
in  toward  the  center  8  inches  and  without  disturbing  the  upper 
forms  resting  on  the  posts,  /. 


TRA/M5VER5E  5ECT1O/M. 


-  — *—  — — "~"^|      'h'ttt  Hahn  Pairs  tf'o*..  frfrodo* 

,.      •_     •          *         »__     Irrfrfjt*.    _ 


or  UPPER  ARcn~~p/y.  MALP 

FIG.  71. — Penstock  reinforced  with  Kahn  Bars. 

To  take  out  the  forms  the  lower  forms  were  moved  toward 
the  center  and  removed.  Then  one  half  of  the  upper  forms 
was  taken  out  by  dropping  the  side  at  g,  first. 

The  section  to  the  left  was  that  built  where  the  ice  would 
pound  and  the  half  on  the  right  where  the  penstock  passed 
into  the  excavation. 

Where  the  penstock  left  the  cliff  it  was  carried  on  three 


MATERIALS, 


107 


masonry  piers,  but  where  it  was  rock  up  to  the  bottom  of  the 
penstock  it  was  built  as  shown.  On  the  side  where  there  was 
no  rock  cliff  dowel  pins  were  set  as  shown.  The  rough  surface 


.CROSS  BAR  TO  RESIST    CTF£.CTA 


IISVCRTE..D 

COMT 
AND  GE.NJE.KAL. 


PLAN 


'A          ^ 

.   -SrafTioN  J3-J3., 


FIG.  72. — Types  of  reinforced  floors. 


FIG.  73.— Kahn  bar. 


of  the  rock  was  smoothed  with  concrete  but  no  attempt  was 
made  to  fill  it  up  to  the  gradient. 

The  outer  forms  were  taken  off  in  three  days  and  the  inner, 
in  five  days.     The  weather  was  cool  and  almost  freezing. 


108 


HYDROELECTRIC  PLANTS. 


FIG.  75. 


FIG.  74. — Ransome  system  of  reinforced 
concrete  building. 


runwau jolank 


universal  cement\  v%y?  sacks  per  yd 


i-:?:: 

" 


/e-ffiods  <?*c-c-H 


c !»       *    — <<?x/ —  •        ..^ 

^^g^L?^gfv«g4{S;^p^l 


.    * 

FIG.  76. — Reinforced  concrete  penstock. 


MATERIALS.  109 

The  costs  for  the  first  182  feet  were  as  follows: 
Penstock  resting  on  solid  rock  and  as  shown  in  Fig.  76. 

ITEMIZED   COST   PER   FT. 

Forms,  inner,  making $.67 

Forms,  erecting 57 

Lumber  at  $30  per  thousand 1 . 08 

Steel,  placing  and  hauling 22 

Cement,  5£  sacks 3.00 

Dowel  pins 09 

Sand,  .61  cubic  yards  at  50c 30 

Labor,  mixing,  tamping,  etc 83 

Concreting  rock  bottom,  labor 80 

Washing  inside 07 

$7.63 

COST   PER   YD. 

Concrete,  labor,  mixing,  tamping,  etc $1.36 

Concrete,  cement,  7  sacks 4.40 

Concrete,  sand,  1  cubic  yard 50 

Forms,  making  and  erecting 2 . 00 

Forms,  lumber 1 . 80 

Steel,  .90  Ib.  at  $1.83 1.65 

Steel,  placing 28 

Steel,  hauling 13 

$12.12 
Placing  steel  per  Ib.  (upper)  and  (lower) $.003 

The  second  182  feet  of  penstock  cost  $10.75  per  cubic  yard. 
As  each  182  foot  section  is  built  the  cost  of  the  inner  forms  is 
decreased.  Also,  the  men  become  accustomed  to  the  work  and 
do  it  more  cheaply. 

Where  the  penstock  rested  on  piers  as  shown  in  the  lower  part 
of  Fig.  76,  the  cost  was  as  follows: 

Forms,  lumber $0 . 36 

Forms,  labor  at  $2 27 

Concrete,  labor 1 . 14 

Concrete,  cement,  6  sacks 3. 30 

Sand 50 

Steel,  placing 27 

Steel,  175  Ib.  at  $1.83 3.20 

$9.04  per  yard. 

In  the  above  work  the  bottom  was  difficult  to  get  to,  hence 
the  high  cost  of  labor  on  concrete. 


110  HYDROELECTRIC  PLANTS. 

Where  the  penstock  was  carried  over  piers,  the  cost  per  foot 
was  as  follows: 

Part  above  bottom $5 . 80 

Bottom 2. 17 

Piers  18  in.  thick  and  average  height  30  in. .    1 .00 

$8. 97  per  foot- 

The  intake  at  the  inlet  of  penstock  contained  59  yards  con- 
crete and  5,000  pounds  steel.     The  form  work  was  quite  diffi- 
cult, consisting  of  floor,  beams  and  10  in.  walls. 
The  cost  of  concrete  was  as  follows: 

Forms,  labor $1 . 00 

Forms,  lumber 0.00 

Concrete,  labor 78 

Concrete,  cement,  7  sacks 3.85 

Concrete,  sand 50 

Concrete,  washing  and  trimming 15 

Steel,  .85  Ibs,  at  $1.83 1 . 56 

Steel,  placing 26 

A  reinforced  concrete  abutment  140  feet  long  and  about 
16  feet  high  cost  per  yard,  as  follows: 

Forms,  labor 96 

Forms,  removing  and  trimming 23 

Forms,  lumber  (old) 00 

Steel,  45  ftr> 82 

Steel,  placing 10 

Cement 3.30 

$5.45  per  yard. 

The  power  house  was  entirely  of  reinforced  concrete  and 
built  for  three  35  in.  turbines  under  a  head  of  13  feet.  Each 
turbine  is  in  a  separate  wheel  pit.  The  walls  are  mostly  10  in. 
and  16  in.  thick. 

The  cost  of  the  concrete  in  the  power  house  was  as  follows: 

Forms,  labor \$2.12 

Forms,  lumber 2 . 00 

Pump 40 

Concrete,  labor 2 . 00 

Concrete,  cement 3 . 30 

Sand 50 

Washing  and  trimming  concrete 10 

Steel,  at  $183 , 1 . 10 

Steel,  placing .50 

$12.02  per  yard. 


MATERIALS. 


Ill 


The  forms  in  all  cases  were  carried  up  full  height  of  the  struc- 
ture before  the  concrete  was  placed.  While  this  costs  more  for 
lumber  work  is  much  more  rapid.  The  above  power  house 
was  built  in  three  weeks,  and  in  winter  weather. 

BUILDING    BLOCKS. 

There  are  now  on  the  market  many  patent  moulds  for  making 
concrete  building  blocks,  but  there  is  no  reason  why  the  engineer 
should  not  make  his  own  moulds,  as  it  frequently  happens  that 
it  is  desired  to  make  many  special  blocks. 

In  Fig.  77  is  shown  a  mould  which  is  easily  made,  and  which 
gives  good  results  and  a  cheap  block.  The  face  board  A  has 
fillets  D  nailed  to  it  to  from  the  joints  as  shown.  The  sides E  are 
set  up  and  the  spacing  boards  F  slipped  into  the  grooves  formed 


0838& 


FIG.  77. 

by  the  fillets  on  the  facing  boards  and  the  corresponding  slits 
in  the  side  boards.  The  face  of  the  facing  boards  is  lined  per- 
fectly smooth  with  metal  before  the  fillets  are  nailed  on.  All  the 
wood  which  comes  in  contact  with  the  concrete  must  be  thor- 
oughly soaked  in  oil  to  prevent  warping  and  sticking  to  the 
concrete. 

Both  sides  of  the  spacing  boards  should  also  be  lined  with 
iron.  When  the  mould  is  all  assembled  the  clamps  G  are  put  on, 
then  mortar  1  to  2  is  poured  in  so  that  it  stands  at  the  top  edge 
of  the  fillets.  The  concrete  (mixed  rather  damp)  is  then  filled 
in  so  that  it  comes  about  up  to  the  centre  of  the  cores  H.  The 
cores  are  then  pressed  down  between  the  spacing  boards  and 
into  the  concrete  and  the  mould  then  filled  up  over  and  around 
the  cores.  The  cores  should  be  covered  with  sheet  metal  or 


112  HYDROELECTRIC  PLANTS. 

made  entirely  of  it.  These  are  put  in  the  mould  by  guess,  a  half- 
inch  one  way  or  the  other  making  no  difference.  The  facing 
plank  should  be  two  or  three  inches  thick,  and  can  be  from  12 
to  14  or  16  feet  long.  When  filled,  the  mould  should  be  left  for 
at  least  four  days,  when  the  clamps  are  knocked  off,  the  blocks 
taken  out  and  the  cores  driven  out.  The  cores  should  have  a 
slight  taper.  One  of  the  good  points  of  this  mould  is  that  the 
face  of  the  block  is  at  the  bottom  of  the  mould,  so  that  it  is  an 
easy  matter  to  get  a  fine,  smooth  face  on  the  block.  Where  the 
face  is  formed  in  a  vertical  position  there  is  sure  to  be  a  difference 
in  the  hardness  and  color  of  the  top  and  bottom  edges.  The 
moulds,  while  drying,  must  be  sprinkled  twice  a  day  and  kept 
shaded  from  the  sun.  A  1-3-5  mixture  makes  a  strong  enough 
block  for  all  ordinary  purposes. 

If  desired,  projections  may  be  put  on  the  spacing  boards  so 
that  there  will  be  cavities  in  the  blocks  to  fill  with  mortar  while 
laying,  thus  binding  the  whole  wall  more  strongly  together. 

The  actual  cost  of  these  blocks  is  from  10  to  12  cents  per  super- 
ficial square  foot.  A  wall  built  of  building  blocks  and  nine 
inches  thick  equals  a  brick  wall  13  inches  thick.  To  lay  a 
nine-inch  wall  which  would  have  the  same  superficial  area 
as  a  13-inch  brick  wall,  using  1000  bricks,  would  cost  £7. 

By  adding  about  J  to  3  per  cent,  of  red  iron  oxide  by  weight 
to  the  cement  sand  (1  to  1  mixture),  the  concrete  blocks  may 
be  made  to  represent  sandstone.  Ultra-marine  blue  added 
in  the  same  proportion  produces  a  slate  or  bluish  limestone 
effect.  The  strength  of  the  concrete  is  slightly  increased  by  the 
coloring  matter.  Ultra-marine  green  and  vermilion  can  also  be 
used. 

Bus  hammering  the  surface  of  the  concrete  gives  it  a  fine 
appearance,  and  only  costs  1J  to  2  cents  per  square  foot. 
A  wall  of  blocks  will  require  one-fourth  the  mortar  and  one- 
third  the  labor  that  a  13-inch  brick  wall  will. 

A  brick  wall  13  inches  thick,  faced  with  pressed  brick,  will 
cost,  per  superficial  square  foot,  as  follows  : 

7  pressed  brick  @  $30  per  1000 $0.02  per  square  foot 

14  common  brick  @  $10  per  1000 14    " 

Mortar  and  Labor .30 

Total..  .65    " 


MATERIALS.  113 

The  same  wall,  built  of  building  blocks  would  cost  from  15  to 
to  20  cents  per  square  foot.  It  takes  one-third  cubic  yard  of 
mortar  to  lay  100  blocks  24x8x8  inches,  and  a  mason  should 
lay  ten  blocks  per  hour.  Labor  and  mortar  costs  four  to  five 
cents  per  superficial  square  foot. 

STRENGTH  OF  MATERIALS. 

It  is  the  purpose  of  the  author  to  here  give  a  clear  and  concise 
treatment  of  the  subject  without  going  into  laborious  explana- 
tions and  complicated  reasoning.  The  engineer  wants  the 
strength  of  a  beam  or  column  and  wants  it  quick.  It  does  not 
matter  if  the  result  is  not  exact  so  long  as  it  gives  a  reasonable 
degree  of  accuracy. 

DEFINITIONS. 

A  moment  at  a  given  point  is  the  product  of  a  force  and  the 
distance  between  the  given  point  and  the  point  of  application. 

The  neutral  line  is  a  line  which  passes  through  that  part  of  the 
section  in  which  there  is  no  strain,  neither  compression  nor 
tension. 

The  moment  of  inertia  of  a  section  about  a  certain  axis  is  the 
sum  of  the  products  of  the  elementary  particles  of  the  section 
and  the  square  of  their  distance  from  that  axis. 

The  moment  of  resistance  of  a  section  is  the  quotient  obtained 
by  dividing  the  moment  of  inertia  by  the  distance  of  the  outside 
fibers  (in  which  the  strain  is  a  maximum)  from  the  neutral  line. 

The  radius  of  gyration  of  a  section  is  the  distance  from  the 
axis  at  which  the  sections  if  concentrated  would  have  the 
same  moment  of  inertia  as  before. 

SYMBOLS. 

P   =  Concentrated  safe  load  at  any  point. 
p    —  Safe  pressure  per  square  inch  of  area  for  columns. 
A    =  Area  of  section  in  square  inches. 
F   =  Factor  of  safety. 

W  =  Load,  uniformly  distributed,  in  pounds  =  total  safe  load 
H- weight  of  beam. 

L    =  Length  of  clear  span  in  inches. 
/     =  Length  of  column  in  inches. 
M  =  Bending  moment,  in  inch  pounds,  any  section. 
d    =  Depth  or  height  of  section  from  out  to  out,  in  inches. 


114  HYDROELECTRIC  PLANTS. 

n  =  Distance  of  center  of  gravity  of  section,  from  top  or 
from  bottom  in  inches. 

5  =  Safe  stress  per  square  inch  in  extreme  fibers  of  beam 
either  top  or  bottom,  in  pounds  according  as  n  relates  to  distance 
from  top  or  from  bottom  of  section  =  safe  strength. 

D   =  Maximum  deflection,  in  inches. 

/  '=  Moment  of  inertia  of  the  section,  neutral  axis  through 
the  center  of  the  section. 

R  =  Section  modulus  =  moment  of  resistance.  'Given  in 
tables  for  standard  sections.) 

r     =  Radius  of  gyration,  in  inches. 

E   =  Modlus  of  elasticity. 


GENERAL   FORMULAS. 


Beams  : 


a    *  *•  l       IT 

__S.  R--.  r-^ 


-S/-SR    S  -—   -  — 
IT  /      -R 


Steel  columns  in  buildings 


p  =  17100-57- 


Steel  struts  in  trusses 


p  =  13500-50  — 


Wrought  iron  columns 

9000 


p  - 


36000  r2 


MATERIALS. 


115 


TABLE  XXVIII. 
STRENGTH  OF  MATERIALS  IN  POUNDS  PER  SQUARE  INCH. 


E 
VIodulus  of 
Elasticity 

Ultimate 
Strength 
per  square  inch. 
(Tension) 

Ultimate 
Strength 
per  square  inch. 
(Single  shear) 
across  grain) 

Ultimate 
Strength 
per  square  inch. 
Columns,  etc. 
(Compression) 

Ultimate 
Strength 
or  Beams, 
Flecture 

Ash  

1,600,000 

16,000 

6,800 

5,000 

Beech 

1,300,000 

11,500 

7,000 

5,000 

Birch  

1,400,000 

15,000 

8,000 

480 

Brass,  cast  

9,200,000 

18,000 

10,300 

Brass,  wire  

14,2000,00 

49,000 

Cedar  

3,500 

Chestnut  

1,000,000 

4,000 

320 

Copper,  cast.  .  . 

18,000,000 

30,000 

Copper,  wire  .  .  . 

18,000,000 

60,000 

Concrete,  6  mos. 

old  

0 

700 

Concrete,  1  year 

old  

0 

1,000 

Elm  

1,000,000 

4,200 

Glass  

8,000,000 

Iron,  cast  

12,000,000 

16,000 

20,000 

80,000 

33,000 

to 

to 

23,000,000 

100,000 

Iron,  cast,  aver- 

age   

17,500,000 

100,000 

Iron,  wrought  \ 

18,000,000 

50,000 

47,000 

36,000 

bars,  sheets  ( 

to 

and  plates    ) 

40,000,000 

Iron,  wire  

26,000,000 

56,000 

Iron,  wire  ropes 

15,000,000 

Lead,  sheet  .... 

720,000 

3,300 

Granite  

8,000  to 

32,000 

(  1,000,000 

2,000  to  10,000 

400 

t4,000 

4,000 

Oak  (white)  

3    to 

to 

to 

/  2,000,000 

700 

7,000 

Oak,  average.  .  . 

1,500,000 

Pine,  white.  .  .  . 

1  ,  GOO,  000 

7,000 

200  to  500 

t   750     f3,500 

3,200 

Pine,  yellow.  .  .  . 

1,600,000 

1  2,000 

250  to  600 

t!400     t5,000 

5,400 

Spruce  

1,600,000 

8,000 

200  to  500 

t  600     t4,000 

3.700 

Hemlock  

6,000 

3,000 

3,000 

Steel  bars  

29,000,00 

45,000 

45,000 

64,000 

to 

to 

to 

42,000,000 

120,000 

120,000 

Steel,  average.  . 

35,500,000 

100,000 

60,000 

Oregon  Pine  

4,500 

Sycamore  

1  ,000,000 

4,000 

Brick  and  ce- 

ment   

280 

1,000 

Limestone  

2,600  to  18,000 

750 

Sandstone  

2,800  to  16,000 

1,000 

Best  Leather 

belting  

1,000 

t  Cross  grain. 


116 


HYDROELECTRIC  PLANTS. 


C/2 


ii  <N 

> 


(N 


Sec 


T^ 


hk 


MATERIALS. 


117 

! 


I 


^ 


• 


118 


YDROELECTRIC  PLANTS. 


i 


tp 


f  IN 
-,  + 


X 


X 


X 


2 


(N 


MATERIALS. 


119 


CO 


Bj 


Sect 


120 


HYDROELECTRIC  PLANTS. 


BEAMS. 

Mr.  A.  L.  Johnson  gives  the  following  method  for  designing 
reinforced  concrete  beams: 

All  beams  are  considered  as   being   12  inches  wide  and   as 

having  e  =  — .      (See  Fig.  78.) 

For  ordinary  concrete  of  1-3-6  mixture  or  where  1-2-5  is  used 
but  the  mixing  not  of  the  best,  so  that  the  modulus  of  elasticity, 
Ec  of  the  concrete  =  3,000,000  per  square  inch,  and  where  Es 
the  modulus  of  the  steel  =  29,000,000  pounds  per  square  inch. 
Elastic  limit  of  the  steel  50,000  pounds  per  square  inch.  //  = 
200,  fc  =  2000. 


Then  yl  =  .33lh;~-j-    =  .64    per   cent.  =  percentage  of    the 


r-^-l 


j a*/* 

-i 


.  78. 


whole  area  of  beam  which  is  steel,  wherein  d  =  spacing  of  bars 
and  a  =  area  of  one  bar. 

MQ  =  3620  h2  =  resisting  moment  =  M  F,  where  F  is  the 
factor  of  safety  used,  and  M0  =  bending  moment. 

For  a  better  grade  of  concrete  such  as  would  be  made  of 
trap  rock,  good  gravel  or  good  limestone  in  the  proportion  of 
1-2-4,  and  well  made.  In  this  case  E,  the  modulus  for  the  con- 
crete, =  2,400,000.  fc  =  the  compressive  strength  (breaking)  = 
2400  pounds  per  square  inch,  ft  =  tensile  strength  of  the  con- 
crete 200  pounds  per  square  inch  and  the  same  values  for  the 
steel  as  the  above. 


MATERIALS 


121 


Then,  yl  -  .418  h  =  -j-  =  .132*  =  1.1  per  cent. 

M0  =  5505  /i2  =  M  F. 

In  the  above,  F  should  be  taken  at  5  or  6.  M  =  bending 
moment  in  inch  pounds  for  beam  loaded.  (See  case  4,  page  123.) 

EXAMPLE: — A  beam  12  inches  wide  and  of  10  foot  span  sus- 
tains a  uniform  load  of  20  feet  of  water.  Find  the  necessary 
area  of  the  reinforcing  bars:  mixture  good,  and  of  1 :2:4  concrete. 

TABLE  XXIXa. 

TABLE  FOR  USE  IN  DESIGNING  REINFORCED  CONCRETE  BEAMS. 
A.  L.  JOHNSTON.      BEAMS  12"  WIDE.    1:2:5  CONCRETE. 


M0 

h* 

<7t 

MO 

h 

Q 

50,000 

3.00 

.397 

1,000,000 

13.4 

1.77 

100,000 

4.24 

.530 

1,500,000 

16.4 

2.17 

150,000 

5.20 

.687 

2,000,000 

19.0 

2.50 

200,000 

6.00 

.793 

2,500,000 

21.25 

2.80 

250,000 

6.71 

.886 

3,000,000 

23.25 

3.00 

300,000 

7.33 

.971 

3,500,000 

25.10 

3.32 

350,000 

7.94 

.048 

4,000,000 

27.00 

3.55 

400,000 

8.48 

.120 

4,500,000 

28.50 

3.76 

450,000 

9.00 

.188 

5,000,000 

30.00 

3.97 

500,000 

9.48 

.252 

5,500,000 

31.5 

4.16 

550,000 

9.94 

.313 

6,000,000 

33.00 

4.34 

600,000 

10.38 

.373 

6,500,000 

34.25 

4.52 

650,000 

10.81 

.428 

7,000,000 

35.50 

4.69 

700,000 

11.22 

.482 

7,500,000 

36.75 

4.85 

750,000 

11.61 

.535 

8,000,000 

38.00 

5.01 

800,000 

12.00 

.585 

8,500,000 

39.00 

5.17 

850,000 

12.36 

.633 

9,000,000 

40.25 

5.32 

900,000 

12.72 

1.68 

9,500,000 

41.5 

5.47 

950,000 

13.07 

1.726 

10,000,000 

42.5 

5.60 

*  h  is  the  depth  of  beam  in  inches  from  top  to  bottom  surface  of  concrete, 
t  q  is  the  area  of  steel  in  square  inches. 

The  load  W  =  12,600.     Neglecting  dead  load  of  beam. 
S       =  .132  h  =  1.1  percent.     M  =  5505  h2  =  M  F. 


M0  = 


5(12600X10X12) 


5505  W  =  945,000,  and  h  =  13  inches.     The  area  of  the  steel 
then  is,  13  inches X  12  inches  X  .011  =  1.71  square  inches. 


122  HYDROELECTRIC  PLANTS. 

These  formulas  will  serve  for  any  reinforcing  which  is  especially 
prepared  to  prevent  slipping.* 

Tables  giving  safe  loads  on  floors  and  beams  may  be  had 
from  the  various  companies.  The  Trussed  Concrete-Steel 
Company  of  Detroit  publish  a  useful  booklet. 

COLUMNS  AND  FOUNDATIONS. 

Numerous  experiments  seem  to  indicate  that  columns  made 
of  reinforced  concrete  and  less  than  20  to  25  diameters  in  height 
do  not  fail  by  flexture  (bending)  but  invariably  crush.  There- 
fore under  these  conditions  the  column  need  not  be  calculated 
for  flexture.  The  crushing  strength  of  the  concrete  may  be 
taken  at  from  1500  pounds  per  square  inch  to  1800.  Using  a 
factor  of  safety  of  5  to  6  we  have  the  safe  strength  of  250  to  350 
pounds  per  square  inch.  Concrete-steel  columns  wound  with 
wire  or  hooped  may  have  a  safe  strength  of  800  to  1400  pounds 
per  square  inch. 

The  building  ordinances  of  Chicago  allow  a  maximum  load 
on  concrete  of  8  to  15  tons  per  square  foot.  Trautwine  gives 
the  crushing  strength  as  follows: 

For  concrete    1  month  old  12  to    18  tons  per  square  foot. 

6       "         "    48  "     72     " 
12       "         "    74  "   120     " 

Kidder  gives  14J  tons  per  square  foot  as  the  safe  load. 
A  factor  of  safety  of  irom  6  to  10  should  be  used. 
Crushing  strength  for  neat    (all  cement)   cement  =  25  to  60 
tons  per  square  foot. 


*The  author  has  lately  been  using  nothing  but  plain  round  mild  steel 
bars  which  may  be  purchased  for  about  $0.018  per  pound  delivered. 
One  and  one-fourth  per  cent,  of  mild  steel  is  used  in  this  case,  and  in  all 
cases  where  rods  lap  the  ends  pass  each  other  40  diameters. 

Where  high  carbon  rods  are  used  they  stretch  long  before  their  full 
strength  is  utilized,  and  the  concrete  cracks.  Therefore  the  only  value 
of  the  more  expensive  steel  is  lost. 


MATERIALS. 


123 


TABLE  XXX. 

PROPERTIES  OF  BEAMS. 


Bending 
Moment 

M  max 

Max. 
Load 

Pressure 
at  Support 
P* 

Deflection 
D 

Case  (1) 

P  L 

S  R 

p 

PL9 

U  L-dr3 

L 

3EI 

Case  (2) 

^QOOOOOOO 

WL 

5  R 

P 

WL3 

^.        -L           .1 

2 

2L 

8  E  I 

Case  (3) 

Q 

PL 

45  R 

P 

PL9 

R^  L  fc^ 

4 

L 

2 

48  El 

Case  (4) 

OOOOQOO 

WL 

85  R 

P 

b     WL9 

P  L  *d 

8 

L 

2 

384    El 

Case  (5) 

0 

Pab 

SRL 

P  b       Pa 

P  L9  a2  b* 

It^*-^ 

L 

ab 

L°T   L 

3EIL* 

Case  (6) 

£>      ft 

P  a  (L  -  a) 

2SRL 

P 

2PL3a2(L-o)2 

lr±-L-k^ 

L 

a  (L  -  a) 

2 

3  E  I  V 

Case  (7) 

P  (2  b  +  LJ 

i  '     £l                    ' 

2L 

&)  —  L  —  gd 

2  KS-P5  a 

or 

P  (2  a  +  LJ 

2  L 

NOTE. — All  lengths  are  measured  in  inches,  and  all  forces  in  pounds. 
The  moments  of  resistance  and  inertia  will  be  found  under  the  prop- 
erties of  sections. 


124  HYDROELECTRIC  PLANTS. 

TABLE  XXXI  (Kidder). 
SAFE  BEARING  LOAD  FOR  DIFFERENT  SOILS  IN  TONS  PER  SQUARE 

FOOT. 

Minimum.   Maximum 

Rock,  hardest  kind 200 

Rock,  equal  to  Ashler  masonry 25  30 

Brick,  equal  to  Ashler  masonry 15  20 

Brick,  of  poor  quality 4  7 

Clay  in  thick  beds,  always  dry 4  6 

Clay  in  thick  beds,  moderately  dry 2  4 

Clay  in  thick  beds,  soft  and  wet 1  2 

Gravel  and  coarse  sand 8  10 

Sand,  fine  and  compact 4  6 

Sand,  fine,  clean  and  dry 2  4 

Alluvial  soils  and  uncertain  sand 0.5  1 

Safe  pressures  are  given  by  Rankine  to  be  1  to  1J  tons  pel 
square  foot  on  tamped  earth;  2  to  3  tons  per  square  foot  on 
compact  gravel  and  dry  sand ;  or  4  to  6  tons  per  square  foot 
where  a  few  inches  settlement  may  be  allowed;  1  to  2J  tons 
per  square  foot  safe  load  no  pure  soft  clay ;  2  tons  per  square 
foot  on  silty  soil  will  settle  3  to  12  inches  in  a  few  years. 

TABLE  XXXII   (Kidder). 

MAXIMUM  SAFE  LOAD  IN  POUNDS  PER  SQUARE  INCH  ON  DIFFER- 
ENT KINDS  OF  MASONRY  FOR  BEARING  PLATES  UNDER  COL- 
UMNS AND  GIRDERS. 

For  granite 1000 

best  grades  of  sandstone 700 

soft  sandstone 400 

"    hard  stone  rubble 150  to  250 

extra  hard  brick  in  cement  mortar 150  to  200 

good  hard  brick  (Eastern)  in  cement  mortar.  .  .  .  120 

common  brickwork 100 

"    good  Portland  cement  concrete 200 

"    good  Portland  cement  concrete  reinforced 400 

One  or  more  holes  through  bottom  of  column  bearing  plates 
should  be  left  so  that  it  can  be  determined  whether  or  not  the 
grout  fills  up  underneath. 


MATERIALS. 


125 


FACTORS   OF   SAFETY. 

The  factor  ot  safety  is  that  figure  by  which  the  ultimate 
strength  is  divided  in  order  to  get  the  safe  strength,  and  there- 
fore is  the  most  important  of  all  engineering  data.  The  reck- 
less engineer  adopts  a  low  factor  of  safety  trusting  to  luck  for 
future  fame  as  a  close  calculator  while  the  conservative  engineer 
selects  the  higher  values.  It  is,  therefore,  largely  a  personal 
equation. 

In  Table  XXXIII  the  factors  of  safety  are  given  as  recom- 
mended by  Un»win,  Gordon,  etc.,  and  Pencoyd,  Carnegie  &  Cam- 
brian Steel  Companies.  They  are  very  conservative;  judgment 
must  be  exercised  in  their  use  however.  Where  the  material 
is  exposed  to  wear  or  rust  a  certain  amount  of  the  area  must  be 
allotted  to  this  loss  and  the  factor  applied  to  the  remaining 
portion.  If  samples  of  the  materials  are  frequently  tested,  a 
much  lower  factor  may  be  used  based  on  these  tests. 

TABLE  XXXIII. 
FACTORS  OF  SAFETY. 


Name  of  Material. 

Steady  Load, 
No  Vibration 
Dead  Load. 

Fluctuating 
Loads. 
Vibrations. 

Shocks 
as 
Machine. 

Temporary 
Structure. 

Tensile 
Dead 
Load. 

Steel  

5 

5  to  7 

15 

4 

8  to  12 

Cast  Iron  

6 

15 

20 

Very 

uncertain 

Steel  Shafting  

5 

8 

12 

4 

Leather  Belts  

10 

12 

14 

6 

Stay  Bolts  

6 

7 

12 

4 

.. 

Wood  Dry  

6 

12 

20 

8 

10 

Wood  Green  
Brickwork 

15 
15 

18 
25 

30 
30 

12 
14 

Steel  Columns  

6 

6  to  10 

12 

3 

Nickel  Steel  

5 

5  to  7 

10 

3 

8 

Bronze  

5 

6 

8 

3 

7 

EXAMPLES. 

In  nearly  all  pocket-books  there  are  tables  giving  the  proper- 
ties of  standard  sections  of  structural  steel  and  "Sample's." 
"  Properties  of  Steel  Sections  "  gives  the  properties  of  all  sorts 


126 


HYDROELECTRIC  PLANTS. 


of  built-up  sections*.     It  is  assumed  that  the  reader  possesses 
such  a  table  in  solving  the  following  examples: 

Beams. 

EXAMPLE  l.-^Given  a  24-inch  I-beam  of  16-foot  span  weighing 
100  pounds  per  foot:  what  is  the  safe  uniform  load  it  will  sustain? 
From  the  tables  for  standard  section,  7  is  2380;  n,  the  distance 
of  the  neutral  axis,  A  A  from  the  extreme  fibers  is  12  inches, 
therefore  (Fig.  79) 

*-£-!»tal9M 

• 

R  is  given  in  the  tables  in  the  column  headed  Section  Modulus. 
From  case  (4), 

857? 
Load    = 


where  16,000  -  safe  strength  of  the  steel. 
25  R       2X1-6000X198.3 


W  = 


3L 


3X1*6" 


132,200  Ibs. 


' 

FIG.  79 


FIG.  80. 


Q    ^-    7~>  c\    C*     TO 

The   difference  between  — = —  and      '    .    is   due    to    the   fact 

L  o  L 

that  the  equations  in   properties   of   sections  gives   inch  pound 

SS  R        2SR 
values  thus  ^j-        —j-. 

If  the  beam  is  built  up  as  shown  in  Fig.  80,  and  we  have  no 
tables  giving  the  value  oil  or  R,  I  may  be  found  as  follows: 

The  moment  of  inertia  of  any  built-up  section  about  an  axis 
is  equal  to  the  sum  of  the  moments  of  inertia  of  those  sections 
through  whose  centers  of  gravity  the  axis  may  pass,  plus  the 
sum  of  the  moments  of  all  sections  through  whose  centers  of 
gravity  the  axis  does  not  pass,  plus  the  area  of  all  such  sections 
multiplied  by  the  square  of  their  distances  from  the  axis. 


*With   permission   of   the    publishers   several   of    Sample's  tables  are 
given  in  Chapter  IX. 


MATERIALS. 


127 


EXAMPLE  2. — Find  /  for  Fig.  (80),  first  about  the  axis  m  n, 
which  passes  through  the  center  of  gravity  of  I-beam  (l),and 
is  at  the  distance  n  from  the  center  of  gravity  of  (2)  and  (3), 
then  1=1  for  beam  (1)+ 2  [area  of  beam  (2)  or  (3)  Xn2]  +2 
(moment  of  inertia  of  beam  2  or  3). 

Figured  on  this  axis,  the  load  should  be  in  the  direction  of 
the  arrow,  because  the  neutral  axis  passes  at  the  point  where 
there  is  neither  tension  nor  compression. 


1 


FIG.  81.  PIG.  82. 

In  the  case  of  the  axis  passing  through  the  center  of  gravity 
of  all  the  members  as  in  Fig.  (Si),  I  =  [moment  of  inertia  of 
the  I-beam]  +  2  [moment  of  inertia  of  one  of  the  two  channel 
beams.] 


FIG.  83.  FIG.  84. 

Care  must  be  exercised  in  selecting  /  for  the  various  sections, 
as  in  the  tables  /  is  given  for  both  axes. 

In  the  case  of  a  latticed  beam,  Fig.  82,  the  lattice  is  not  con- 
sidered. Thus  7  =  twice  the  /  for  one  channel. 

For  Fig.  83 

/  =  2  I   —  —  -  -f  b  t  nn   I  +  4  [(area  of  angle  Xn2)  +  (/  of  angle)] 


, 
r 


The    distance  X,    Fig.  84,  is  foUnd  by  deducting  the  values 


128  HYDROELECTRIC  PLANTS. 

given  in  tables  for  standard  sections  for  the  perpendicular  dis- 
tance from  center  of  gravity  to  back  of  flanges,  from  the  dis- 
tance y. 

I  for  two  angles  (Fig.  84)    =  twice  I  for  a  single  angle. 

EXAMPLE  3.  —  Find  the  safe  center  load,  P,  which  two 
4x4xJ-inch  angles  will  support.  Span  =  6  feet,  Z  =  1  inch. 

From  case  (3),  P  =  ~r^~ 


From  tables  for  standard  sections,  7  on  axis  1,  1.  =5-56. 
Therefore  7  for  the  two  angles  =  11.12. 


In  the  tables  x  is  given  for  the  above  angle,  as 
18.-,w=d-#=4-l.  18=  2.82 


FIG.  85  . 
11.12  3.94X.16000 


EXAMPLE  4. — Design  the  beam  shown  in  Fig.  85  of  rectangu- 
lar section  made  of  cast  iron.  To  start  with  assume  a  thickness 
b  of  2  inches.  From  Table  XXVIII  the  ultimate  strength  of 
cast  iron  in  flexture,  is  36,000.  The  load  is  to  be  a  steady  stress, 
therefore  the  factor  of  safety  is  6  and  the  safe  strength  is  6,000 
pounds. 

b  d? 
Now  M  =  5  R  or,  W  L  =  6000  —  and  substituting  the  proper 

2   y  d? 

values,  5000X48  =  6000 ^ =  120,  and  d  =  10. 95  inches; 

o 

call  this  11  inches. 


MATERIALS.  129 

To  get  the  depth  at  any  other  point,  say  30  inches  from  the 
end,  proceed  as  before,  only  substituting  30  inches  instead  of 
48  inches. 

In  the  design  of  shafting  we  frequently  have  the  condition 
shown  in  Fig.  80,  and  have  to  find  the  maximum  bending  moment 
M.  Suppose  the  gear  or  pully  weighs  1111  pounds,  and  the  belt 
chain  or  tooth  pull  tending  to  rotate  it,  regardless  of  7  or  r.  p.  m. 
=  4111  pounds,  then 


5  for  steel  is  about  10,000.     Substituting  and  solving  for  d  we 
have  a  shaft  about  5|  inches  in  diameter. 
If  the  wheel  is  at  the  center  of  the  span. 

,,        (4111  +  1111)X(3  +  6)X12        PL. 

M  =  -  -  -  =  —  —  m  inch  pounds. 


I 3'---+^ tf'-. 


FIG.  £6. 

EXAMPLE  5. — A  standard  7  beam,  20  feet  span,  is  loaded 
at  the  center  with  a  load  P,  of  10, COO  pounds.  Find  proper 
size  of  beam: 

From  case  (3)  R  =   3  P  L 


S 
Therefore  3  x  1) 

16,000 

From  tables  for  standard  steel  I-beams  we  find  that  the  section 
having  a  section  modulus  of  37.5  is  a  12-inch-35  pound  beam. 

Columns. 

The  radius  of  gyration  r  =  ^|  -r-  plays  an  important  part 
in  the  design  of  columns. 


130  HYDROELECTRIC  PLANTS. 

If  the  column  is  a  built-up  section  /,  the  moment  of  inertia,  is 
found  in  the  same  way  as  for  beams. 

EXAMPLE  1. — Find  r  about  axis  11,  for  column  (Fig.  87) 
composed  of  two  latticed  12-inch  channels  weighing  40  pounds 
per  foot  each,  and  placed  six  inches  apart. 

/  =  2[(area  of  each  channel  X  by  X2)  +  (/  for  each  beam)] 

From  tables  for  standard  channels  we  find,  x  for  axis,  11, 
and  a  12  inch-40-pound  channel  to  be  .  722,  therefore  X  =  .  722 
+  3  inch,  or  3.722  inches:  area  of  channel  =11.76.  7  for  one 
one  channel  =  6.63. 

Substituting, 

1=2  (11.76X3.722  +  6.63)  =  339 


[/  |      339  =      9 

'*  A      "\2X11.76 


lr          r  n 

-4J_ 


FIG.  87.  FIG.  88. 

Example:  The  column  shown  in  Fig.  88,  is  built  up  ol   four 
3x3xJ-inch  angles.     Find  r 
I  =  4[(area  of  one  angle  X^2)  +  (7  for  one  angle)] 

From  tables  for  standard  shapes  x  ==  .  84. : 
A' =5  — .84=4.16. 
Area  of  one  angle  =  1 . 44.    I  for  one  angle  =  1 . 24. 


104.6 


7  ==  4(1. 44X4. 162f  1.24)  =  104.6        r  =  ^        i  44  =  4-26 
DESIGN  OF  MACHINE  ELEMENTS. 

THE  SCREW. 

F  =  forc'e  in  pounds  applied  at  circumference  of  hand  wheel 
A  at  a  point  B,  R  inches  from  center  line  of  screw.  P  =  the 
distance  between  threads  in  inches  =  pitch  of  screw  =  distance 


MATERIALS. 


131 


which  one  complete  revolution  of  hand  wheel  will  raise  screw. 
W  =  weight  lifted. 

W  P 

Then  F    '  £283* 

where  6.283  =  a  constant. 

EXAMPLE. — What  pull  must   be  applied  at   B  to  just  raise 
5000  pounds  hanging  to  the  screw?     The  screw  itself  weighs 
111  pounds  and  has  a  pitch  of  one  inch.     R  =  24  inches.     /  =  .2 
Then 

Weight  of  screw Ill 

Friction  due  to  screw,  111X.2 22.2 

Weight  lifted 5000.0 

Friction  due  to  the  weight,  5000X.2 1000.0 


And  F  = 


6133.2X1    W 


.6133.2 


6.283X24  =  40.7  pounds. 


FIG.  89  and  90. 

A  man  turning  the  wheel  A  would  exert  an  equal  pressure 
on  each  side  and  in  the  above  case  would  exert  20.35  pounds 
pressure  with  each  hand. 

The  work  of  lifting  is  measured  in  foot   pounds  and  in  the 


70 

above  case  would  =  40.7  X  2  x  —  X  N  where  2  n 


is  the 


circumference  of  the  hand  wheel  in  feet  and  N  the  revolutions. 

A  man  can,  for  a  minute  or  two,  perform  work  equal  to  17280 

foot  pounds  per  minute.     In  the  above  example  one  revolution 

=  40.7X12.566  =  511.4  foot  pounds,  and  the  number  of  revo- 

17280 

lutions  a  man  could  turn  the  wheel  per  minute  =  „—  ^    -  =  33.8. 

511.4 


132  HYDROELECTRIC  PLANTS. 

In  33. S  revolutions  the  screw  would  lift  the  weight  33.8  XP 
or  in  the  above  case  2.82  feet. 

Often  the  screw  itself  does  not  move  vertically,  but  is  sup- 
ported on  a  collar  C,  Fig.  90,  the  nut  attached  to  a  weight 
traveling  along  the  screw  and  lifting  the  weight  W.  In  this 
case  the  friction  of  the  collar  is  added  to  that  of  the  nut  D. 

Knowing  the  pitch  of  the  screw  and  the  weight  it  is  to  sus- 
tain, it  is  a  simple  matter  to  design  it  for  strength.  From  the 
table  giving  the  shearing  strength  of  materials  the  safe  strength 
for  the  material  in  the  threads  is  found  and  sufficient  area  is 
provided  so  that  the  threads  will  not  strip.  If  it  is  six  inches 
in  diameter  at  the  root  of  the  thread  and  the  thread  is  one  inch 
thick  (see  Fig.  91),  the  safe  strength  of  the  thread  making  one 
turn  around  the  shaft  would  be  6X~Xl  inch  X  5  where  5  = 


safe  strength  of  the  metal,     The  same  reasoning  would  apply 
to  the  nut. 

WINCHES. 

Heavy  winches  usually  employ  the  worm  and  gear,  Fig.  92 
for  at  least  one  power  increase. 

L  is  the  distance  in  inches,  a  tooth  on  worm  gear  moves  in  one 
revolution  of  screw.  For  a  one  threaded  worm  L  =  P  for  a 
two  threaded  worm  L  =  2  P,  three  threaded  L  =  3  P,  there- 
fore, for  a  two  threaded  worm  and  a  gear  of  50  teeth  the  shaft 
A  will  make  one  complete  revolution  for  every  25  of  the  crank 
C;  or  disregarding  friction  one  pound  exerted  at  C  should  lift 
25  at  B  a  distance  2  P.  If  the  worm  is  single  threaded  the 
ratio  would  be  1  to  50  and  the  distance  moved  P. 

Efficiency  of  a  worm  gear  is  about  40  per  cent,  for  starting 


MATERIALS.  133 

loads;  50  per  cent,  for  pitch  line  velocity  of  10  feet  per  minute; 
SO  per  cent,  for  velocities  of  100  feet. 

Therefore,  in  the  above  case  of  50  teeth  in  gear  and  single 
threaded  worm  of  J  pitch,  P,  R  =  7  inches,  we  would  have  the 
force  F,  applied  at  C,  necessary  to  start  the  worm  against  a 
resistance  at  the  pitch  line  at  B,  of  2000  pounds, 
,.,       2000XJX1.6 

F  =-*5&xr-  =36-6p°unds- 

1.6  is  gotten   from  the  efficiency  being  40  per  cent. 

36.6  pounds,  acting  at  the  7-inch  radius,  travels  3.665  feet 
per  revolution.  It  requires  48  revolutions  to  raise  the  gate 
24  inches,  therefore  if  the  gate  is  to  be  raised  in  one  minute, 
36 . 6  X  3 . 665  X  48  =  6432  foot  pounds  per  minute  are  required, 
which  is  less  than  half  the  »power  a  man  can  exert  for  short 
periods. 


FIG.  92. 

For  steady  work  during  several  hours,  a  man  can  only  exert 
about  3500  foot  pounds  per  minute. 

Now  if  the  rope  lifting  the  weight  is  run  over  a  smaller  wheel, 
A,  say  ^  the  diameter  of  B,  the  leverage  will  be  increased  in  the 

D 

proportion  of  — r-  ;  but  the  time  of  lifting  is  also  increased  in  the 

same  proportion;  36.6  pounds  at  C  will  now  lift  8000  pounds 
at  A.  If  a  pinion  is  placed  at  A  and  a  spur  gear  D  is  used,  the 
lifting  power  on  the  pitch  circle  F  will  be  increased  in  proportion 
to  the  ratio  of  the  gears.  Suppose  this  ratio  is  1  to  4  in  the 
above  axample,  then  the  36.6  pounds  exerted  at  C  will  lift 
2000X4  or  8000  pounds  at  F.  The  efficiency  of  a  pair  of  well- 
cut  gears  should  be  97  per  cent.,  and  that  of  uncut  and  poorly 
designed  gear  90  per  cent.  Therefore  the  power  delivered  at 

A ,  in  the  abo^e  example  =  2000  X  -^  X  efficiency  of  gears,  or  if 


134  i     HYDROELECTRIC  PLANTS. 

the  pitch  diameter  of  A  =  J  that  of  B,  and  the  diameter  of  E  is 
i  that  of  Z),  8000  pounds  will  be  transmitted  at  .a  loss  of  3  to  10 
per  cent ;  if  10  per  cent  is  lost  7,200  pounds  will  be  the  actual 
weight  lifted  at  F,  and  so  on  through  any  number  of  reductions. 
Force  is  increased  at  the  expense  of  motion,  when  the  energy 
remains  constant. 

HOISTING    BY    ROPE    OVER    A    DRUM. 

5  =  stress  in  rope  in  pounds  at  A  Fig.  93.  When  the  weight 
W  is  suddenly  lifted,  owing  to  slack  in  the  rope,  the  stress  is 
greatly  increased. 

R  =  weight  of  the  whole  rope  in  pounds. 

F  =  equivalent  friction  in  pounds  =  weight  of  all  moving 
parts  x  by  /. 

/  =  coefficient  of  friction. 


FIG.  93. 

Then  5  =  2  W  +  R  +  F. 

W  =  weight  lifted. 

/  =   .01  for  vertical  hoisting  and  .02  to  .04  for  inclined. 

EXAMPLE  :  Required  size  of  rope  to  hoist  vertically,  5,000 
pounds  through  1500  feet;  S  =  [(5000X2)  +  (2 X  1500)]. 01  (5,000 
4-3,000)  ==  13080  pounds. 

If  the  factor  of  safety  =  7  select  rope  having  ultimate  strength 
of  100,000.  (See  table  LXIII). 

If  the  hoisting  is  done  on  an  incline,  S  =  (2  W  +  R)  sin  a  +  F 
and  F  =  f  (W  +  R)  cosine  «.  See  Fig.  93. 

As  the  rope  passes  over  the  drum  the  strain  is  greatly  increased, 
due  to  the  bending  of  the  fibres.  If  the  drum  is  45  times  the 
diameter  of  rope  the  bending  strain  =  8/9  of  the  whole  strain 
on  rope  and  leaves  1/9  of  the  ultimate  load  available.  If  80 
times  the  diameter  of  rope  the  bending  strain  will  have  1  (5  of 


MATERIALS.  135 

the  ultimate  strength  of  the  rope  available  for  use.     The  bending 
stress  on  different  ropes  are  given  in  the  tables. 

STEEL    CABLES. 

E  =  28,500,000  =  modulus  of  elasticity. 

A  =  net  area  of  steel.     R  =  radius  of  drum  or  sheave. 

d  =  diameter  of  each  wire  in  the  rope. 

The  net  working  stress  for  which  the  rope  is  safe  will  then 
be  the  difference  in  S,  found  as  above,  and  the  safe  strength 
given  in  Table  LXIII  for  the  particular  rope. 

EXAMPLE:  Find  safe  load  for  a  one-inch  cast  steel  rope  run- 
ning over  a  six-foot  sheave.  From  Table  LXIV  the  bending 
stress  =  9937  pounds  and  from  Table  LXIII  the  maximum  safe 
stress  for  a  one-inch  rope  =  22667  pounds.  The  difference,  12730 
pounds,  is  the  safe  working  load. 

The  stress  due  to  weight  of  rope  and  weight  lifted  as  found 
by  the  first  formula  for  S  must  not  exceed  this  safe  load 

PULLEY    OR    GEAR. 

When  we  have  a  pulley  or  gear  transmitting  power  we  usually 
wish  to  know  the  tension  on  the  belt  or  rope,  in  case  of  a  pulley 
or  the  pressure  on  a  tooth  of  a  gear. 

EXAMPLE  :  —  A  pulley  38  inches  in  diameter  runs  at  116  revolu- 
tions per  minute,  and  transmits  110  horse  power.  What  is  the 
pull  at  the  rim? 

110X33,000 


38X.  2618X116 

.2618  =  a  constant. 

If  a  gear  has  the  same  diameter  at  the  pitch  circle  the  pressure 
would  be  the  same  and  would  be  considered  as  all  acting  on  one 
tooth. 

CENTRIFUGAL    FORCE    IN    WHEELS. 

Let  W  ••=  weight  in  pounds  of  entire  rim  of  pully,  gear  or 
fly  wheel.  R  =  radius  in  feet  to  center  of  gravity  of  rim  section. 
Sr  =  revolutions  per  minute. 

S  =  total  strain  on  the  cross  section  of  rim  in  pounds.     Then 

5=   .00005427  WxRXSr2. 

S,  divided  by  the  area  of  the  section  gives  the  strain  on  the 
metal  per  square  inch. 


136 


HYDROELECTRIC  PLANTS. 


SHAFTING. 


Consider  one  end  of  the  shaft,  A  Fig.  94,  fast  and  on  the  other 
end  a  lever  /  inches  long,  with  a  weight  of  W  pounds.  Suppose, 
for  example,  we  give  the  shaft  a  safe  strength  5  of  10,000  pounds 


per  square  inch,  then  the  formula  for  the  safe  diameter  under 
that  stress  is  Wl  =  .196d3X  10,000;  from  this  d  may  be  found, 
or  having  d,  S  may  be  obtained. 


FIG.  95. 

For  square  shafts  (Fig.  95)  W  I  =   .28J35 
For  hollow  shafts   (Fig.  95)  W  I  =  A  D^f- 

\  =  area  of  circle  of  diameter  D. 
a  =  area  of  circle  of  diameter  d 
For  maximum  bending  moment  see  Table  XXX. 


CHAPTER  V. 
HYDRAULIC      CONSTRUCTION 

PILING 

No  feature  of  engineering  work  is  more  disappointing  and  at 
the  same  time  more  important  than  piling.  There  is  always 
more  or  less  uncertainty  as  to  the  cost  before  beginning,  and 
then  as  to  the  efficiency  of  the  job  when  completed.  Many 


I 

FIG.  96 


times  piles  will  appear  to  drive  all  right,  when  in  reality  they 
are  being  sheared  off,  as  in  Fig.  96.  Sheet  piles  may  look  well 
at  the  top,  when,  in  fact,  there  are  large  holes  between  them 
further  down. 

There  are  two  patent  types  of  wooden  sheet  piling,  the  Wake- 


FIG.  97. 


FIG.  98 


field  (Fig.  97),  and  the  Beardsley  (Fig.  98).  The  Wakefield 
consists  of  three  planks  all  of  the  same  width,  while  the  Beards- 
ley  pile  is  composed  of  two  widths. 

Each  pile  has  its  advantages  for  certain  conditions.  The 
planks  for  the  Beardsley  pile  being  in  two  widths  are  sawed  out 
of  the  log  to  better  advantage  than  if  all  of  the  same  width. 

137 


138 


HYDROELECTRIC  PLANTS. 


Where  the  pounding  will  not  be  too  heavy,  the  planks  may 
be  spiked  together  with  60d  wire  spikes,  and  clinched,  but 
generally  four  to  eight-  .  five -eighth-inch  carriage  bolts  are 
used.  Of  course,  the  groove  of  one  pile  must  be  slightly 
wider  than  the  tongue  of  the  next,  otherwise  it  will  bind  in  driv- 
ing. The  usual  method  in  the  case  of  the  Wakefield  pile  is  to 
place  a  three-sixteenths-inch  shim  at  a.  The  narrowest  planks 


FIG.  99. 


in'the  Beardsley  pile  are  all  sawed  three-sixteenths-inch  thicker 
than  the  wide  plank  to  get  the  desired  result. 

It  requires  great  experience  and  a  good  head  to  successfully 
drive  sheet  piling.  Experience  with  round  piling  alone  is  worse 
than  none,  as  far  as  sheet  piling  is  concerned.  Each  pile  must 


FIG.  100 

be  given  just  the  proper  edge  bevel,  as  at  a  (Fig.  99),  or  side 
bevel  as  at  b.  The  edge  bevel  causes  the  pile  to  hug  to  the  pre- 
ceding one,  but  if  too  much  is  given  the  piling  may  get  to  run- 
ning in  the  direction  of  the  line  A  B.  The  side  bevel  6, 
is  given  where  the  previous  pile  has  run,  as  shown  by  the 
line  B  C.  If  the  bevel  is  too  great  the  foot  of  the  pile  may  run 
out  of  the  groove.  The  top  of  the  pile  is  held  securely  against 


HYDRAULIC  CONSTRUCTION.  139 

the  preceding  pile  by  the  rope  D,  which  passes  back  to  the  steam 
wench,  in  the  case  of  a  steam  driver,  or  to  a  pair  of  double  blocks 
in  the  case  of  a  horse  driver.  Too.  great  a  pull  on  this  rope  will 
throw  the  foot  of  the  pile  out. 

If  the  pile  runs,  as  shown  in  Fig.  100,  one  or  more  peavies  are 
used  to  bring  it  back  into  line.  Timbers  E,  E  are  laid  along  the 
line  and  bolted  together  with  spacers,  F,  F  between,  to  aid  in 
keeping  the  piling  straight,  as  the  piling  approaches  the  spacers, 
a  bolt  is  put  through  the  timbers  and  the  pile  nearest  the  spacer 
and  the  spacer  removed.  One -inch  bolts  should  be  used  with 
heavy  washers,  so  that  the  timbers  may  be  brought  back  into 
place  rF"they  have  spread  any. 

It  is  often  necessary  to  put  iron  points  on  the  piling,  as  at 
M,  Fig.  99.  These  may  consist  of  iron  2x4-inch,  bent  to  fit  the 
bevel.  The  common  dimensions  of  the  plank  are  2x12  inches  and 


f  Vz'ao/teJ 

-.rt-^  wfi---..-..-.r  s.  =.i  i  i:  ^.-.-.-Jtf's 
7rrj".rs-------.-^.---.---i^^i1ivrw*.a. 


FIG.  101. 

2x8  inches,  and  the  wood  used  may  be  beach,  oak,  Southern  pine, 
gum,  hard  maple,  cypress,  elm,  or  any  close-grained  hard  wood. 
The  head  of  the  pile  should  be  banded  with  a  band  of  the  best 
Norway  iron  £x3  inches,  and  several  bands  should  be  used,  so 
that  two  or  three  banded  piles  will  always  be  ready  for  use. 
Where  the  piling  is  quite  long,  say  25  to  40  feet,  it  must  be  much 
heavier,  and  is  made  as  in  Fig.  101.  Strips  (a)  are  bolted  to  the 
pile  with  J-inch  carriage  bolts  to  form  the  tongue  and  groove. 

PILE    DRIVERS. 

The  smaller  drivers  are  usually  operated  by  horse-power, 
but  for  large,  quick  work  a  steam  driver  is  used,  the  pile 
driver  being  similar  to  the  horse  power,  except  that  the  engine 
is  set  in  the  frames.  The  most  rapid  and  satisfactory  pile 
driver  is  the  steam-head  driver.  The  parts  work  between  the 
leaders  the  same  as  a  drop  hammer,  but  rests  continually  on  top 
of  the  pile.  The  piston  and  weight  are  caused  to  reciprocate  by 


140 


HYDROELECTRIC  PLANTS. 


steam  acting  on  a  piston  in  the  cylinder,  at  the  rate  of  80  strokes  or 
less  per  minute.  The  rapidity  of  hitting  may  be  nicely  regulated. 
Piling  may  be  driven  in  quicksand,  hard  pan,  etc.,  with  this 
driver,  where  it  would  be  impossible  with  the  slower  type.  In 
quicksand  the  pile  is  buoyed  up  by  an  amount  equal  to  the 
weight  displaced,  and  where  the  blows  are  few  and  far  between 
the  pile  rises  between  strokes;  but  with  the  steam-hammer 
the  weight  is  on  the  pile  at  all  times  and  blow  follows  blow  in 
such  rapid  succession  that  the  displaced  particles  of  sand  and 
water  do  not  have  time  to  settle  back 'into  place.  Also  much 
cheaper  grades  of  wood  may  be  used  for  the  piling,  as  the  splinter- 
ing effect  is  less. 

A  common  horse-power  pile  driver  with  a  2CCO-pound  drop 
hammer  costs  all  complete  from  &1£0  to  £200.  The  same  outfit, 
with  a  suitable  boiler  and  engine,  will  cost  from  $800  to  $1,CCO. 
A  steam-head  driver  of  the  same  comparative  size  will  cost 
from  $1,500  to  $3,000. 

COST    OF    DRIVING    PILING. 

TABLE  XXXIV. 
COST  OP  DRIVING  ROUND  WOOD  PILING  AND  NUMBER  DRIVEN  PER  DAY. 


Horse  Power. 

Steam. 

Steam-Hammer. 

Depth 
in 
Compact 
Clay. 
(Feet) 

Depth 
in 
Strong 
Gravel. 
(Feet) 

Depth 
in 
Wet 
Sand. 
(Feet) 

No. 
of  Piles 

Cost 
per  Pile 

No. 
of  Piles 

Cost 
per  Pile 

No. 
per  day 

Cost 

6  to  12 

$1.75 

8  to  10 

$3.50 

15  to  30 

$1.50  to  $2. 

20 

12  to  14 

$5  to  $6 

?5  to  35 

4  to  6 

$2  to  $2.50 

6  to  8 

$4  to  $6 

20  to  50 

$*  to  $1.50 

14 

8  to  10 

$2.50  to  $3 
$2.50 

12 

13 

$2.75* 

16 

*  Labor  was  high. 

The  above  costs  do  not  include  the  pile  itself,  and  represent 
costs  actually  attained  on  various  jobs. 

The  cost  of  driving  sheet  piling  is  about  the  same  per  foot, 
measured  across  the  stream,  as  that  of  round  piling.  It  will 
cost  about  $1.50  per  foot  width  to  drive  12  to  16-foot  piles,  when 
the  driving  is  easy,  and  from  $2.50  to  $3.00  where  it  is  hard. 


HYDRAULIC  CONSTRUCTION. 


141 


The  lowest  average  bid  for  driving  round  piling  on  a  large 
pile  dam  by  several  reliable  contractors  was  45  cents  per  foot  of 
pile.  This  included  the  pile  and  the  sawing  off  under  water. 
The  current  was  strong  and  driving  average.  The  piles  cost 
from  10  to  15  cents  per  foot.  In  charging  so  much  per  linear 
foot  (the  usual  method)  the  pile  is  measured  from  its  point  to 
the  sawed-off  head,  the  penetration  not  being  measured,  though 
it,  of  course,  influences  the  price. 

Ordinary  round  piles  for  hydraulic  work  should  not  cost  more 
than  8  to  15  cents  per  linear  foot  for  driving. 

METHOD    OF    DRIVING. 

Fig.  104  shows  a  few  of  the  common  pile  points  for  round  piles. 
The  first  is  a  soft  iron  strap  and  the  second  and  third  are  of  cast 
iron. 


FIG.  104. 


The  author  has  found  that  for  soft  soils  such  as  sand,  silt,  and 
soft  clay,  the  piles  drive  much  better  if  not  pointed  at  all,  but 
left  with  a  square  end;  in  fact,  experience  with  the  round  piling 
indicates  that  the  large  end  should  be  the  down  end  in  such  soils. 

Sand  is  somewhat  like  a  liquid,  and  has  a  buoyant  force, 
which  will  always  act  to  force  the  pile  out  of  the  ground,  and 
depends  entirely  upon  the  volume  of  the  pile  submerged.  When 
the  pile  is  driven  point  first  this  force  lifts  it  out  as  fast  as  it 
can  be  driven,  but  when  driven  butt  first  tnis  force  acts  in  the 
same  way,  but  is  opposed  by  a  great  frictional  resistance  which 
would  have  to  be  overcome  before  the  pile  could  be  removed. 

This  resistance  represents  the  work  which  would  have  to  be 
done  in  displacing  the  shaded  volume  of  sand  (Fig.  105.) 

Western  rivers,  such  as  the  Platt  and  Elkhorn,  demonstrated 
that  it  was  far  better  practice  to  drive  the  piles  with  the  butt-end 


142  HYDROELECTRIC  PLANTS. 

down.  Of  course  in  this  case  the  small  end  must  be  of  good 
proportions  so  as  not  to  break  or  broom  under  the  hammer. 
With  this  way  the  pile  does  not  spring  back,  and,  instead  of  the 
"  flare  "  hitting  towards  the  sand,  it  drives  away  from  it. 

When  the  pile  driver  is  mounted  on  a  scow,  scattered  round 
piles  may  be  driven  twice  as  rapidly  as  on  land,  but  when  the 
piling  is  along  the  edge  of  a  platform  or  mat,  the  cost  is  less  for 
the  land  driver. 

A  heavy  hammer  and  short  fall  is  the  most  satisfactory,  as 
the  pile  will  be  shattered  less  and  more  blows  can  be  given.  This 
is  especially  true  for  quicksand. 


FIG.  105. 

Trautwine  gives  the  adhesive  power  of  ice  to  a  pile  as  30  to 
40  pounds  per  square  inch  of  surface. 

The  friction  of  a  metallic  pile  is  about  three-tenths  that  of 
wood 

jet  Driving. 

The  most  successful  way  to  sink  round  or  sheet  piling  in  wet 
sand  is  by  means  of  a  jet  of  steam  or  water.  The  author  had  an 
experience  with  the  Elkhorn  River  in  Nebraska,  which  thor- 
oughly demonstrated  the  value  of  the  jet.  After  vainly  trying 
to  drive  sheet  piles  in  the  sand  of  the  river  bed  for  two  months, 
with  an  ordinary  pile  driver,  an  Edson  pile  sinking  outfit, 
costing  about  $150  was  used.  This  is  shown  in  Fig.  106.  Two 
men  handled  the  1-inch  tube,  which  was  constantly  moved  about 
so  as  to  loosen  up  the  sand  under  and  around  the  pile.  Two 
men  worked  the  pump  and  two  men  guided  the  pile.  The  pile 
was  handled  in  the  leaders  of  a  pile  driver,  and  a  2,000-pound 
hammer  left  resting  on  the  head  of  the  pile.  When  the  pile 
stuck,  a  few  blows  of  the  hammer  started  it  again.  With  this 


HYDRAULIC  CONSTRUCTION. 


143 


simple  outfit  an  average  of  from  20  to  30  piles,  14  feet  long  by 
12  inches  in  diameter,  were  driven  per  day,  at  a  cost  of  $1.50 
per  pile. 

Steam  can  be  used  in  the  place  of  the  water.  Jetted  piles 
may  be  of  the  soft  wood.  With  the  jet,  round  piles  averaging 
14  inches  in  diameter  can  be  sunk  by  means  of  a  strong  jet  at 
the  rate  of  a  foot  per  second.  Large  cylinders  may  be  rapidly 
sunk  in  the  worst  sands,  and  it  seems  very  strange  that  this 


FIG.  106. 

method  is  not  more  generally  adopted.     Of  course,  the  jet  can 
only  be  used  for  sands,  or  other  soft  soils. 

CONCRETE    PILES. 

Wooden  piles  rapidly  decay  unless  entirely  submerged  in 
water.  If  exposed  to  sea  water  they  are  eaten  up  by  insects. 
Concrete  piles  are  permanent,  and  it  is  only  a  question  of  a  few 
years  when  wooden  piles  will  be  a  curiosity,  having  been  entirely 
displaced  by  the  concrete. 

There  are  several  patent  concrete  piles,  a  noteworthy  one 
being  the  Raymond  pile.  This  is  made  by  sinking  a  thin  casing 
of  metal  the  size  of  the  pile  and  filling  it  with  concrete.  Fig.  107 
shows  the  adaptation  of  the  concrete  pile,  and  how  eight  concrete 
piles  displaces  22  wooden  piles.  Reinforcing  bars  may  be 
placed  in  the  molds  before  filling. 


144 


HYDROELECTRIC  PLANTS. 


Fig.  108  illustrates  a  concrete-steel  pile,  which  is  made  before 
placing  it  in  the  ground.  As  here  shown  it  is  reinforced  by 
three  f-inch  Kahn  bars,  making  160  pounds  of  steel  for  a  20-foot 
pile.  At  the  bottom  end  of  the  pile  the  three  rods  converge  to 


oooo oo ooooo 

oocoooooooo 


FIG.  107. 

a  point,  and  are  welded  together.  The  concrete  used  is  made  of 
high-grade  Portland  cement  and  clean  river  gravel,  in  the  pro- 
portion of  1  to  3. 

The  method  of  constructing  the  piles  is  as  follows:    The  molds 
or  forms  are    set  up    on  one    corner,  and    the    concrete  placed 


FIG.  108. 

in  them.  Piles  can  be  built  in  this  way  in  lengths  varying 
from  16  to  26  feet,  as  required.  When  molded  complete  the 
pile  is  left  to  set  for  about  a  day,  without  water,  and  then  kept 
in  the  form  for  a  week  longer,  with  continual  sprinkling.  By 
that  time  the  concrete  has  hardened  sufficiently  to  allow  the 


HYDRAULIC  CONSTRUCTION. 


145 


piles  to  be  lifted  out  of  the  form  and  set  away  for  another  period 
of  a  week  or  more,  during  which  time  they  are  kept  constantly 
wet.  After  this  they  can  be  removed  for  transportation  or 
storage. 

The  piles  can  be  driven  by  steam  hammers  weighing  as  much 
as  5000  pounds,  with  a  fall  of  about  5  feet.  The  head 
of  the  pile  is  protected  from  damage  in  driving  by  a 
cushion  cap  made  of  alternate  layers  of  iron  plate,  wood  and 
lead,  which  is  clamped  to  the  pile  head.  This  cap  also  serves  to 
guide  the  pile  in  the  leads.  Such  a  pile  20  inches  across  corners 
at  the  top  and  6  inches  at  the  bottom  would  cost  about  $9.00 
all  complete,  and  give  the  bearing  power  of  four  wooden  piles. 


Protection  of  wooden  piling  from  the  Teredo  can  be  secured 
by  grouting  a  concrete  jacket  around  the  pile  after  it  is  in  place, 
as  shown  in  Fig.  109. 

STEEL    PILING. 

Within  the  last  few  years  there  has  been  a  startling  advance 
made  in  the  construction  of  piling,  due  chiefly  to  the  advent 
of  the  steel  pile.  One  of  the  best  known  steel  piles  is  that  made 
by  the  Interlocking  Steel  Sheeting  Company  of  Chicago,  and 
called  the  Jackson  pile.  Fig.  110  will  sufficiently  explain  the 
style  and  use  of  this  pile.  Great  depths  may  be  obtained  by  its 
use,  and  by  using  concrete  to  fill  between  the  channels,  it  may 
be  made  absolutely  water-tight.  Of  course  the  cost  of  this  pile 
is  great,  a  linear  foot  of  12-inch  pile,  if  made  of  the  lightest 


146 


HYDROELECTRIC  PLANTS. 


;  channels  and  I-beams,  will  weigh  72  pounds,  which  would 
•make  the  cost  of  steel  at  two  cents  per  pound,  about  $1.50  per 
foot.  Steel  piling  costs  about  $40  per  ton  f.o.b.  factory.  How- 
ever, they  may  be  withdrawn  and  driven  many  times,  thus 
bringing  the  cost  down  to  a  reasonable  figure.  Almost  every 
form  in  steel  has  now  been  worked  into  sheet  piling  and  patented, 
but  the  author  gives  one  to  the  public  which  is  not  patented  and 


FIG.  110. 

which  possesses  some  good  features.  (See  Fig.  111.)  In  this 
pile  Phoenix  columns,  boiler  plates  and  angle-irons  are  used.  The 
columns  act  as  stiffeners  to  the  webs  formed  by  the  boiler  plates. 
Any  width  plate  may  be  used  and  corners  turned  by  simply 
bending  the  plate.  The  column  may  be  of  any  size  and  can  be 
filled  with  concrete.  The  weight  per  foot  of  a  pile  12  inches 


FIG.  111. 

'wide  is  34  pounds,  which,  at  three  cents  per  pound,  would  cost 
$1.02  per  foot  of  pile.  By  using  a  5f-inch  Phanix  column  the 

pile  will  weigh  25  pounds  per  foot. 

i 

IRON    PILING. 

..  The  cast  iron  pile  is  used  to  quite  an  extent  where  the  iron 
.alone  is  depended  on  for  supporting  the  load  and  resisting 
.corrosion,  The  smaller  iron  piles  are  usually  sunk  by  means 
-.of  a  screw.  Fig.  112.  The  screw  has  about  one  complete  turn,  and 


HYDRAULIC  CONSTRUCTION. 


147 


is  from  18  to  60  inches  in  diameter.  The  shaft  usually  consists 
of  a  piece  of  heavy  shafting.  Though  in  the  pile  shown  in  Fig. 
113  a  hollow  27-inch  cast  iron  shell  1£  inches  thick,  and  made 
in  7-foot  sections  was  used.  These  large  ^iles  were  driven  by  the 


FIG.  112. 

Erie  railroad  for  the  purpose  of  sustaining  a  tunnel  under  the 
Hudson  River.  A  large  ratchet  and  pawl  (Fig.  113),  driven 
by  two  hydraulic  cylinders,  was  used  for  screwing  down  the 


V     m      m 


FIG.  113. 

pile,  each  cylinder  tested  to  1500  pounds  pressure  per  square 
inch.  A  dead  load  of  440,000  pounds,  placed  on  top  of  the  pile 
was  found  necessary  to  cause  the  5-inch  screw  to  penetrate 
35  feet,  and  40  revolutions  were  made.  One  pile  was  driven  (ex- 


148  \      HYDROELECTRIC  PLANTS. 

elusive  of  all  such  work  as  placing  new  sections,  etc.)  in  10  hours. 
Under  a  test  load  of  500,000  pounds  for  15  days  and  600,000 
pounds  for  another  month,  the  pile  settled  a  little  over  J  inch. 

SAND  PILES. 

Sand,  the  great  foe  to  pile  driving,  is  made  to  act  as  a  pile 
in  some  cases  where  the  soil  is  treacherous.  A  large  wooden 
or  steel  pile  is  driven  six  or  eight  feet  in  the  mud,  and  then  pulled 
out.  The  hole  thus  left  is  filled  with  sand,  well  tamped  in  place. 
The  hole  may  be  dug  like  a  well  and  then  filled.  The  particles 
of  sand  transmit  the  load  equally  throughout  the  area  of  the  hole. 

Another  form  of  pile  which  can  be  used  in  sandy  and  gravelly 
soils  is  made  by  jetting  down  a  IJ-inch  gas  pipe  having  perfora- 
tions at  the  lower  end  about  J  inch  in  diameter,  and  then  forcing 
through  it  a  cement  grout,  the  tube  being  slowly  withdrawn. 
This  fills  the  interstices  in  the  soil  and  forms  a  concrete  pile  of 
from  12  to  48  inches  in  diameter.  Sand  which  is  too  compact 
cannot  be  successfully  cemented  in  this  wa\ . 

BEARING    POWER   OF    PILES. 

The  bearing  power  may  be  approximately  determined  by  the 
formula  (Trautwine) : 

VFallinltTxWt.  of  Hammer  in  Ibs.  X  .023 

Extreme  Load  =  -  — — - .- : — — 

Last  sinking  in  inches  -f  1. 

The  safe  load  would  be  one-fourth  to  one-tenth  this. 

Great  caution  must  be  observed  in  driving  piles  meant  to 
sustain  important  loads,  which  would  be  injured  by  settling. 
A  pile  may  drive  into  sand  with  great  resistance  but  under  a 
steady  load  settle  rapidly.  The  earth's  crust  is  full  of  strata 
of  varying  density  and  unless  test  borings  are  made  down  past 
the  foot  of  the  pile,  it  may  be  resting  immediately  over  a  strata 
of  silt  or  quicksand. 

Maj.  J.  Sanders,  United  States  Engineer,  gives  the  following 
formula  for  obtaining  the  bearing  power: 

W_n 
8  d 

where  P  —  Safe  load  on  pile  in  pounds. 
W  —  weight  of  hammer  in  Ibs. 

n  =  fall  of  hammer  in  inches. 

d  =  penetration  in  inches  caused  by  each  of  the  last  few  blows. 

The  objection  to  this  last  formula  is  that  the  selection  of  the 


HYDRAULIC  CONSTRUCTION.  149 

factor  of  safety  is  not  left  to  the  engineer.  However,  as  his 
experiments  were  made  in  river  mud  on  the  Delaware  River, 
the  factor  of  safety  should  be  about  ten  in  which  case  this 
formula  gives  a  much  larger  safe  load  than  does  Trautwine. 
The  Engineering  News  formula  is  simple  and  safe  and  will  serve 
as  a  check  on  other  estimates.  Safe  load  in  tons  is 

2  X  wt.  of  hammer  in  tons  X  fall  of  hammer  in  ft. 
Penetration  of  pile  in  ins.  for  last  blow  +  1  in. 

When  the  pile  is  driven  to  rock  or  unyielding  hard  pan  it 
acts  as  a  column  and  can  be  figured  as  such. 

A  grillage  is  placed  over  the  heads  of  piles  to  distribute  the 
load  evenly  on  each  pile  as  in  Fig.  114.  Steel  beams  may  also 
be  used. 


FIG.  114. 

A  more  permanent  way  to  distribute  the  load  is  by  the  use 
of  concrete  placed  a  foot  or  so  deep  around  and  over  the  heads 
of  the  piling  as  in  Fig.  107.  Reinforcing  should  be  used  so  that 
if  any  pile  or  cluster  of  piles  settles,  the  foundation  will  hold 
together. 

DRILLING. 
HAND  DRILLING. 

On  small  jobs  hand  drilling  is  much  the  cheapest  and  in  fact 
many  times  on  large  work,  hand  drilling  though  much  slower 
has  been  found  as  cheap  as  power  drilling.  The  two  methods 
used  in  hand  drilling  are  churn  drilling  and  jump  drilling.  In 
jump  drilling  a  comparatively  light  drill  is  held  by  one  man 
and  struck  by  one  or  two  strikers.  The  drill  is  made  of  tool 
steel  one  inch  to  one  and  one-fourth  inch  in  diameter  and 
sharpened  as  in  Fig.  115.  Between  blows  the  drill  is  revolved 
a  quarter  turn. 


150 


HYDROELECTRIC  PLANTS. 


A  short  drill  called  a  starter  is  used  to  start  the  hole.  It  is 
given  a  slightly  larger  diameter  across  the  bit  than  the  finishing 
drills,  the  shoulders  at  (a)  are  made  parallel  and  about  one-half 
inch  long. 

An  eight-pound  striking  hammer  is  used.  A  spoon,  Fig.  116, 
or  a  pump,  Fig.  117,  is  used  to  keep  the  hole  clean.  The  pump 
is  made  of  three-quarter  inch  gas  pipe.  A  marble  b  is  placed  in 
the  bottom  as  shown  and  by  moving  the  pipe  up  and  down, 
water  and  stone  dust  fill  it  and  it  is^then  emptied  by  removing 
from  the  hole. 

When  the  rock  is  seamy,  the  shoulder  a  should  be  lengthened 
and  for  very  difficult  work  a  wing  c,  Fig.  115,  welded  to  each 
side  of  the  drill  will  help  materially.  For  straight  vertical 
drilling,  churn  drilling  is  the  most  satisfactory.  The  body  of 


the  drill  is  made  of  ordinary  iron  1  to  1J  inch  diameter  and  from 
six  to  eight  feet  long.  The  drill  point  or  bit  is  made  of  tem- 
pered steel  welded  to  the  bar.  In  churn  drilling  the  workman 
(often  two)  lifts  the  bar  and  drops  it,  giving  it  a  quarter  turn 
each  blow.  The  weight  of  the  bar  is  relied  on  to  do  the  cutting. 
This  is  the  best  drill  to  use  for  sinking  anchor  bolts  for  dams, 
locks,  etc. 

The  cost  of  drilling  by  hand  depends  on  the  position  of  the 
holes  and  the  character  of  the  rock.  The  author's  experience 
has  been  that  with  jumper  drilling,  holes  1J  inch  in  diameter 
and  24  inches  to  36  inches  deep,  for  anchor  bolts  in  the  beds 
of  streams  can  be  drilled  in  one  hour  with  three  men.  Trautwine 
gives  seven  to  eight  feet  of  1}  inch  hole  in  granite  as  a  fair  day's 
work  for  three  men  and  eight  to  nine  feet  in  marble  or  limestone. 

A  churn  drill  worked  by  one  man  will  drill  about  the  same 
amount  as  a  jumper  with  three  men. 


HYDRAULIC  CONSTRUCTION. 


151 


MACHINE   DRILLING. 

Among  the  machine  drills  the  diamond  drill  ranks  the  highest 
in  rate  of  cutting  and  depth  of  hole,  but  as  it  is  intended  more 
for  mineral  prospecting  or  deep  well  boring,  we  will  not  give  a 


detailed  description  of  it.  A  diamond  drill,  drilling  a  IJ-inch 
hole  200  to  300  feet  deep  costs  about  $1250  and  will  drill  one 
to  two  feet  per  hour  at  a  cost  of  from  $1  to  $2  per  foot. 


162  HYDROELECTRIC  PLANTS. 

The  drill  commonly  used  is  shown  in  Fig.  118.  This  drill 
may  be  worked  with  steam  or  air,  the  only  difference  being  in 
the  packing  of  the  glands.  The  price  of  such  a  drill  varies 
from  $200  to  $500  depending  on  depth  and  diameter  of  hole 
it  will  drill  and  the  depth  of  feed.  The  feed  is  from  12  to  30 
inches  and  this,  limits  the  depth  of  drilling  before  a  longer  drill 
is  put  in. 

If  driven  by  steam  the  steam  pipe  will  have  to  be  one  inch 
for  the  smaller  drills,  1J  inches  for  medium  and  1J  inches  for 
the  large  drill  having  30  inches  feed  and  drilling  a  2-inch  to  5-inch 
hole  27  feet. 


FIG.  119. 

If  driven  by  air  (see  page  192  "  Tunnels  "),  the  operation  of 
the  drill  will  be  understood  by  referring  to  Fig.  118  where 
X32  is  the  hand  feed,  X24  is  the  piston,  X27  the  rifle  bar  which 
causes  the  drill  to  revolve  slightly  each  stroke,  X25  the  rifle 
nut  which  causes  the  rifle  bar  to  rotate  the  bar  and  with  it  the 
ratchet  wheel  X30.  Thus  each  time  the  piston  reciprocates 
along  the  bar,  the  ratchet  turns  a  notch  and  on  the  down  stroke 
the  piston  with  the  piston  rod  and  drill  rotates. 

Extra  charge  is  made  for  the  tripod  which  costs  from  $30 
to  $80  depending  on  the  size  of  the  weight.  Fig.  119  shows 


H  YDRA  ULIC  CONSTR UCTION. 


153 


a  Sullivan   drill   all  complete  except  the  hose  pipe.     Hose  pipe 
suitable    for    the  modern  drills  costs  60  cents  per  foot.     Con- 


FIG.  120. 

nections  will  add  $4  to  this  per  hose.      A  mining  column,  Fig 
121,  for  tunneling  costs  about  $50. 


FIG.  121. 


For  use  in  hard  rock  a  drill  having  a  bit  shaped  like  a  4-  is 
best,  but  for  seamy  rock  where  the  drill  tends  to  bind  it  should 


154 


HYDROELECTRIC  PLANTS. 


be  shaped  like  an  X      In  soft  sandstone  a  chisel  bit  is  recom- 
mended.    Each  drilling  machine  should  have  three  sets  of  drills 


Fip.  122. — Channeler  at  work  on  canal. 

of  three  drills  per  set.     These  cost  $3  to  $5  per  set  for  the 
smaller  drills. 


FIG.  123. — Channeler  at  work  on  tail  race. 

Each  drilling  machine  requires  one  man  to  operate  it  and 
takes  two  to  three  men  to  move  it.     One  man  can  attend  the 


HYDRAULIC  CONSTRUCTION.  155 

air  compressor  plant  or  steam  plant.  One  blacksmith  will 
sharpen  drills  for  five  or  six  machines  if  he  is  provided  with 
special  hammers  which  give  the  correct  form  to  the  bits. 

Among  the  best  drills  are  those  made  by  the  Sullivan  Ma- 
chinery Company,  Chicago,  111.,  the  Ingersoll  Rock-Drill  Com- 
pany,   New    York,    Burleigh    Rock-Drill    Company,    Fitchburg 
Mass.,  and  the  Gray  don  &  Denton  Manufacturing  Company  of 
New  York. 

Only  since  the  Chicago  Drainage  Canal  was  built  has  the 
channeling  machine  come  into  use  for  canal  cutting,  but  since 
then  several  large  hydraulic  plants  have  used  them.  Canals 
cut  with  a  channeling  machine  require  no  lining.  Fig.  122 
shows  a  channeler  at  work.  Where  it  was  not  necessary 
to  preserve  the  rock  for  building  purposes,  the  channeler 
merely  cuts  a  channel  about  one  inch  across  and  six  or  seven 
feet  deep  along  the  edge  of  the  canal,  and  then  the  rock  is 
blasted  out  in  the  usual  way.  This  leaves  a  smooth  surface, 
unshattered  by  the  explosion.  The  drill  is  given  a  slight  slant, 
as  in  Fig.  123,  so  that  the  general  contour  of  the  wall  will  be 
perpendicular. 

The  channeler  shown  in  Fig.  122  costs  about  $2000  with  boiler, 
but  on  a  large  job  the  canal  lining  saved  will  more  than  pay  for 
it.  Such  a  channeler  should  cut  from  100  to  150  square  feet  of 
channels  per  day,  at  a  cost  of  twenty  cents  per  square  foot. 

EXPLOSIVES. 

Dynamite  is  the  most  common  form  of  explosive,  and  is  used 
on  all  kinds  of  work.  It  is  commonly  put  up  in  half-pound  sticks 
wrapped  in  oilei  paper.  These  sticks  are  1J  inches  in  diameter 
and  Q  inches  long.  Any  strength  may  be  had,  the  most  common 
being  from  30  to  40  per  cent,  nitre-glycerine,  up  to  80  per  cent. 

Dynamite  is  ordinarily  quite  safe  to  handle,  though  under 
certain  conditions  it  is  extremely  unstable,  and  should  be  handled 
intelligently.  In  small  quantities  good  dynamite  may  be  burned 
and  this  widely  advertised  fact  has  caused  the  death  of  many 
men.  When  exposed  to  the  sun  or  boiling  water  (as  is  often 
done  when  thawing  it  out)  it  rots.  This  condition  usually,  but 
not  always,  may  be  detected  by  the  appearance  of  a  greenish 
tinge.  In  this  state  it  will  explode  when  burnt  or  even  jarred. 
In  lar^e  masses  dynamite  may  be  exploded  by  its  own  heat 
while  burning. 


156 


YDROELECTRIC  PLANTS. 


Dynamite  will  explode  if  struck  between  irons,  but  not  by 
blows  of  wood  upon  wood.  A  drop  of  pure  nitro-glycerine  may 
ooze  from  a  stick  on  thawing,  and  falling  three  or  four  inches 
explode  on  striking  a  hot  surface.  The  electric  spark  and  also 
lightning  will  explode  dynamite.  We  do  not  give  these  defects 
space  here  to  scare  the  inexperienced,  but  to  make  known  that 
dynamite,  when  rotting,  is  dangerous.  When  in  good  condition 
and  handled  with  any  degree  of  care,  it  is  as  safe  as  any  explosive. 
To  thaw  frozen  dynamite,  place  in  a  warm  place,  but  do  not 
boil. 

To  use  the  dynamite  a  stick  is  opened  at  one  end  (Fig.  124), 
and  with  a  punch  of  the  suitable  size,  a  hole  is  punched  two  or 
three  inches  deep,  as  at  (A).  Then  a  cap  ir  placed  over  the  end 


12.7 


FIGS.  124  to  127. — Preparing  a  dynamite  charge. 

of  the  fuse,  as  in  Fig.  125,  and  the  end  of  the  cap  crimped  down 
on  to  it.  The  cap  is  the  most  dangerous  part  of  the  charge,  and 
great  care  must  be  exercised  to  in  no  way  injure  the  ends  con- 
taining the  fulminate  of  mercury.  In  cutting  the  fuse  off  to 
insert  in  the  cap,  use  a  sharp  knife,  and  be  careful  not  to  spill 
the  powder  out.  Many  failures  are  attributable  to  lack  of 
powder  near  the  fulminate.  The  cap  and  fuse  is  then  pushed 
solidly  into  the  hole  in  the  dynamite,  and  the  loose  paper  around 
the  stick  is  twisted  about  the  fuse  and  tied  solidly  with  string 
(Fig.  126).  If  the  charge  is  under  water,  or  in  a  damp  hole, 
the  exterior  around  the  fuse  and  string  should  be  coated  with 
axle  grease,  soap,  or  some  such  water-proofing  compound.  The 
charge  is  now  placed  in  the  hole  and  tamped  in  on  top,  filling  the 
hole.  Dry  sand  is  the  best  for  tamping,  but  rock  dust  is  also 
good.  The  end  of  the  fuse  is  now  slit  (see  Fig.  127),  and  the 
charge  is  ready  for  firing. 


H YDRA  ULIC  CONSTR  UCTION. 


157 


When  a  charge  fails  to  explode,  great  caution  should  be  ob- 
served in  going  near  it,  as  often  the  fuse  hangs  fire  for  two  or 
three  minutes.  Do  not  tamp  the  holes  with  anything  but 
wood.  Rather  than  attempt  to  dig  out  an  unexploded  stick, 
drill  another  hole  eight  or  ten  inches  from  it  and  fire  another 
charge. 

The  charges  may  be  varied  by  cutting  the  sticks  into  different 
lengths.  Deep  drilling  is  necessary  to  produce  the  best  results. 


D 


_T 


FIG.  128. — Connections  for  electrically  firing  dynamite. 

The  harder  the  material,  the  higher  the  per  cent,  of  nitro-glycer- 
ine  used.  For  soft  clay,  the  holes  are  bored  with  an  ordinary 
two-inch  auger  and  giant  powder  used,  or  mild  15  per  cent 
dynamite. 

On  large  work,  or  where  all  the  charges  must  be  fired  at  once, 
the  charges  are  all  connected  to  an  electric  circuit  as  in  Fig.  128, 


FIG.  129. 

by  turning  the  handle  of  the  magneto  (a)  the  charges  are  all 
exploded,  A  special  cap  is  used.  This  method  is  especially 
good  for  under-water  work. 

When  it  is  desired  to  get  in  an  unusually  heavy  charge,  a 
small  charge,  called  a  "  squib,"  is  first  fired,  making  a  cavity, 
as  at  (6),  Fig.  129.  This  is  then  filled  with  dynamite  taken 
from  the  paper  cases  and  tamped  in.  For  work  under  a  building, 
and  where  it  is  desired  to  avoid  jarring,  about  two  inches  of  a 
stick  is  fired  at  a  time,  the  stronger  grade  of  dynamite  being 
used. 


158  HYDROELECTRIC  PLANTS. 

To  blast  ice,  the  charges  are  placed  several  feet  under  water. 
Large  boulders  may  be  cracked  by  simply  placing  the  charge  on 
top  and  resting  a  heavy  stone  on  the  charge.  Old  piling  may  be 
cut  off  under  water  by  boring  a-  hole  partly  through  and  sticking 
in  the  dynamite.  The  author  once  had  to  drive  sheet  piling 
where  the  sand  was  filled  with  saw  logs  in  some  places  to  a  depth 
of  eight  feet.  A  place  was  cut  through  these  by  driving  two-inch 
gas  pipes,  as  shown  in  Fig.  130.  The  log  was  first  located  with 
a  J-inch  rod ;  in  the  lower  ends  of  the  pipe  were  plugs.  When  the 
pipes  were  driven  the  plugs  were  rammed  out  and  the  charges 
placed  in  the  pipes.  A  rammer  then  held  the  charges  in  while 
the  pipes  were  withdrawn.  It  often  required  two  men  one  day 
to  cut  off  a  large  log,  but  all  were  finally  cut. 


FIG.  130. 

Jovite  is  a  more  modern  production  than  dynamite,  and 
possesses  several  advantages  over  that  explosive.  It  will  burn 
without  exploding;  jarring  will  not  set  it  off.  It  will  not  rot 
and  become  dangerous.  It  can  be  hammered  iron  on  iron  with 
perfect  safety.  For  the  same  strength  it  is  lighter  than  dyna- 
mite. It  may  be  dropped  on  hot  iron.  Lightning  will  not  ex- 
plode it.  It  contains  no  liquid,  as  does  dynamite.  It  cannot 
freeze.  A  stick  may  explode  within  two  inches  of  another  with- 
out exploding  the  latter. 

Dynamite  gives  off  poisonous  fumes,  which  cause  severe 
headaches.  It  has  affected  the  author  to  such  an  extent  that 
walking,  was  impossible.  It  has  even  caused  death.  Therefore, 


* ) 

H  YDRA  U'LIC  CONSTRUCTION.  159 

when  working  with  it  in  tunnels  or  deep  cuts,  the  workmen  do 
not  return  to  the  work  immediately,  but  wait  for  the  clearing 
away  of  the  fumes.  Jovite  does  not  give  off  injurious  fumes, 
and  therefore  much  time  is  saved  in  its  use. 

Jovite  is  put  up  in  sticks,  the  same  as  dynamite,  or  in  bulk.  It 
is  graded  as:  No.  1,  which  has  the  strength  of  20  per  cent,  dyna- 
mite; No.  2  is  equivalent  to  40  per  cent,  dynamite ;  No.  3XX 
equivalent  to  60  per  cent  dynamite.  It  is  exploded  in  exactly  the 
same  way  as  dynamite.  In  bulk  form  it  may  be  used  to  fill 
into  cracks  and  seams,  thus  saving  much  drilling.  To  get  a 
lifting  effect  where  it  is  desired  to  produce  quarry  stone,  No.  1 
is  used,  and  where  the  stone  is  to  be  broken  up  into  small  pieces, 
No.  3XX. 

For  under-water  work  jovite  possesses  no  especial  advantage 
over  dynamite,  except  in  its  safety  before  using.  It  must  not 
be  left  in  the  water  any  great  length  of  time,  as  the  nitrate  of 
soda  leaks  out.  It  can  be  procured  put  up  in  water-tight  bags. 

The  cost  of  jovite  is  slightly  less  than  dynamite  on  account  of 
its  lesser  weight,  the  price  per  pound  being  about  the  same. 

Ordinary  electric  fuses  with  a  cap  attached  and  with  from 
four  to  eight  feet  of  wire  for  each  fuse,  cost  from  $3  to  $4  per 
100.  A  blasting  machine  which  will  fire  20  charges  costs  $25. 
Dynamite  costs  about  14  cents  per  pound  for  the  lower  percent- 
ages of  nitro-glycerine,  and  up  to  16  cents  for  60  per  cent,  nitro 
glycerine. 

CABLEWAYS. 

In  building  long  dams  the  cableway  is  the  best  of  all  methods 
for  handling  materials.  There  are  innumerable  systems  of 
cable  tramways  now  in  use,  but  the  following  are  the  funda- 
mental types. 

Fig.  131  shows  a  splendid  arrangement  for  making  large 
fills.  There  are  a  number  of  cars  A ,  or  skips  which  travel  around 
on  the  stationary  cable  5,  being  moved  by  the  traction  rope  C. 
The  terminal  D  is  the  same  at  both  ends,  one  or  both  being  used 
as  filling  stations.  The  cars  can  be  loaded  automatically  as 
they  pass  around  the  terminal  and  automatically  dumped  at  any 
point  along  the  cable.  Intermediate  supports  may  be  placed 
between  the  terminals.  By  adding  another  rope  which  is  car- 
ried around  with  the  car  or  skip,  and  a  set  of  falls  the  car 
may  be  stopped  at  any  point  and  lowered. 


160 


HYDROELECTRIC  PLANTS. 


Fig.  132  illustrates  the  most  common  form  used  for  construct- 
ing dams,  etc.  The  carriage  is  pulled  along  the  cable  and 
may  be  lowered  at  any  point  by  a  man  stationed  on  the  shore. 
Loads  as  high  as  10  to  20  tons  may  be  handled  on  spans  of 
over  1000  feet.  By  making  the  towers  movable  the  whole 
field  of  operation  may  be  covered. 


FIG.  131. 

FOR  SMOKB-STACK  GUYS,  TROLLEY-LINE  SPAN  WIRE  AND  OTHER  PURPOSES.    COMPOSED 
OF  SEVEN  CAL.  STEEL  WIRES  TWISTED  TOGETHER. 


Price  in  cents 
per  100  feet. 

Diameter  in 
inches. 

Weight  per  100  feet 
in  pounds. 

Approximate  breaking 
strain  in  pounds. 

315 

1/2 

52 

8,320 

250 

7/16 

40 

6,000 

200 

3/8 

30 

4.700 

160 

5/16 

22 

3,300 

115 

1/4 

13 

1,750 

80 

3/16 

8 

1,000 

60 

5/32 

5         / 

700 

45 

1/8 

3.50 

375 

35 

3/32 

2.25 

320 

Fig.  133  shows  a  very  good  plan  where  a  cheap  cableway  is 
desired.  By  simply  varying  the  elevation  of  the  boom  fall 
blocks,  the  bucket  or  skip  may  be  made  to  run  out  over  the  cable 
and  back  again  by  aid  of  its  gravity  alone.  The  dimensions 
given  are  for  a  cablewa.y  built  by  Parker  &  Flynn  of  Waterford, 


HYDRAULIC  CONSTRUCTION. 


161 


162 


HYDROELECTRIC  PLANTS. 


N.  Y.  The  total  span  was  900  feet,  arid  the  load  five  cubic  feet 
of  wet  concrete.  The  cable  was  a  J-inch  st-eel  hoisting  cable. 
This  plan  could  be  well  adapted  to  dan  building.  A  set  of  falls 
would  be  carried  by  the  skip  so  as  to  permit  the  lifting  and  lower- 
ing of  materials.  There  being  no  heavy  towers,  it  would  be  an 
easy  matter  to  shift  the  cable  up  or  down  stream. 


z<Le4A**/ 
ft&^&s  JO. 


&%  _.«. 


FIG.  133. — Gravity  cable  way. 

The  Trenton  Iron  Company  give  tns  following  methods  of 
calculating  the  deflection  in  cable  spans. 

The  deflection  of  the  cable  alone  without  load  at  any  point  x  is 
(See  Fig.  134) 


h  = 


(1) 


for  m  =  n  =  —  (at  the  middle) 


wS2 


4X2t        St 


(2)' 


FIG.  134, 

wherein  h  is  the  deflection  in  feet ;  m,  the  distance  in  feet  from  the 
point  x,  under  consideration  to  one  support ;  n,  the  distance  in 
feet  to  the  other  support;  y,  the  distance  from  the  load  to  the 
nearest  point  of  support;  5,  the  distance  between  support  sin  feet 
w  the  weight  of  the  cable  per  foot  in  pounds;  W  the  load  in 


HYDRAULIC  CONSTRUCTION.  163 

pounds  and  t  the  tension  in  the  cable  in  pounds  per  square  inch. 
The  deflection  due  entirely  to  load  is 

W.n.y 

h  -  -  3 


for  n  -      - 


Wy 

h  =  —  -^- 
2t 


and  for  y  =  -- 


for 


fc  - 


(6) 


The  total  deflection  at  any  point  x  will  be  the  sum  of  these 
two,  thus 


2St 


for  n  m  = 


<8> 

*-i 

w  m  n  +  W  n 


for  n=    S_ 


2 
wS2+2WS 


do) 


164  HYDROELECTRIC  PLANTS. 

If  the  tension  is  desired,  transpose  and  solve  for  t,  thus  in  (10) 

•  t  _ 


BRIDGES. 

The  bridge  in  some  one  of  its  many  forms  enters  so  frequently 
into  the  design  of  hydraulic  plants  that  it  is  deemed  advisable 
to  give  the  design  of  a  few  of  the  more  simple  forms  brief  treat- 
ment here. 


FIG.  135. 

One  of  the  simplest  trusses  is  shown  in  Fig.  135.     This  truss 
is  adapted  to  spans  of  from  30  to  40  feet. 
Total  compressive  stress  on 


D~C 
Total  tensile  stress  on  B  C  or 


Total  compressive  stress  in  D  C  =  W,  wherein  W  is  the  total 
concentrated  transient  load. 


FIG.  136. 

These  formulas  are  for  a  concentrated  load:  For  a  uniformly 
loaded  truss  W  would  be  divided  by  4  in  the  above. 
For  a  truss  with  random  load,  as  in  Fig.  136: 
Total  compressive  stress  on 

A 


Total  tensile  tress  on 

BCXAD 
BC  =ABXCDXW 


HYDRAULIC  CONSTRUCTION.  165 

Total  tensile  stress  in 

ACXDB 


Compressive  stress  in  D  C  =  W. 

For  a  truss,  as  shown  in  Fig.  137,  having  equal  loads  at  two 
points  we  have: 

Total  compressive  stress  on 

AB  = 


V 


FIG.  137. 
Total  tensile  stress  on  A  C  or 

*j>-4f 

Total  tensile  stress  on 


Compressive  stress  on  E  C  or  F  D  =  W 

In  Fig.  138  is  shown  the  truss  Fig.  135,  inverted  and  adapted 
to  a  roof  truss.  As  such,  the  total  load  of  rafters  or  purlines, 
supported  by  the  braces  A  C  and  B  C,  produces  the  same  stress 


.xtv. 


FIG.  138. 

as  would  one-half  the  load  concentrated  at  the  apex  C.  The 
horizontal  thrust  in  the  rafters  at  either  end  equals  the  tension 
in  the  rod  C  D. 

Any  of  these  trusses  may  be  turned  over,  in  which  case  the 
compression  members  become  tension  members. 

When  the  spans  are  longer  than  about  40  feet  a  truss,  having 
a  number  of  panels,  as  in  Fig.  139,  is  used.  This  is  the  Burr 
truss,  and  as  shown  here  has  five  panels.  .  • 


166  HYDROELECTRIC  PLANTS. 

Four-fifths  of  the  total  load  of  truss  and  transient  load  is 
taken  as  being  divided  evenly  between  the  four  points  of  sup- 
port, C,  D,  E  and  F,  One-fifth  is  supported  by  the  abutments. 

Total  compressive  stress  on  A  G  or  B  J  =  2WX 7^-7^- 

(jr  C 

Total  tensile  stress  on  G  C  or  /  F  =  2  W. 

TT    X- 

Total  compressive  stress  on  H  C  or  I  F  =  Wx -^-pr 

fi  L) 

w  _     Total  wt.  of  load  and  truss 
Number  of  panels 

The  diagonals  H  E  and  I  D  receive  no  stress  unless  the  truss 
is  unequally  loaded.  The  rods  H  D  and  /  E  each  sustain  a 


Total  compressive  stress  =  W. 

A  C 
Total  compressive  stress  inG  H  or  /  J  =  2WX  >^- 


Total  compressive  stress  in  H  I  =  3  W  X 


GC 
AC 


GC 


A  C 

Total  tensile  stress  in  A  C  or  F  E  =  2  Wx  ^~ 

(j  G 

A  C 

Total  tensional  stress  in  C  D,  D  E  or  E  F  =  ,3  Wx  ^-^ 

G  C 

For  large  trusses  the  cords  and  even  the  braces  frequently 
have  to  be  built  up.  A  properly  built  up  timber  is  better  than 
a  solid  timber  of  the  same  area,  for  though  the  strength  may  be 
less,  it  will  last  longer,  the  interior  being  ventilated. 

Fig.  140  shows  some  of  the  splices  used  by  the  Pullman  Car 
Mfg.  Co.  and  recommended  by  the  Master  Car  Builders'  Asso- 


HYDRAULIC  CONSTRUCTION.  lt>7 

ciation.  Fig.  141  shows  a  met  hod  of  building  up  a  chord  com- 
posed of  a  number  of  planks,  a,  b,  c,  d,  e,  etc.  The 
leaves,  x,  are  made  of  hard  wood  one  third  the  thickness 


^6/os7<L^ 


*t*Ht 


-^-//— 


W 


*       *     11 


0^/5 


3H 
/Z*\ 


FIG.  140. 


of  the  plank  and  of  a  width  three  times  its  own  thickness.  The 
cast  iron  plates,  O,  are  placed  as  shown,  being  staggered  so  as 
to  weaken  the  chord  as  little  as  possible.  The  strength  of  such 


FIG. 


a  beam  should  be  taken  as  about  two  thirds  that  of  a  solid  beam 
of  the  same  net  area.  Where  the  ends  of  the  plank  come  to- 
gether a  wedge,  y,  is  driven. 


168 


HYDROELECTRIC  PLANTS. 


In  case  of  an  emergency  where  quick  work  is  necessary,  the 
plank  may  be  spiked  together.  Wedges  are  driven  between 
the  ends.  In  all  cases  two  bolts  should  be  used,  each  having  a 
factor  of  safety  of  about  three.  Then  if  one  rod  should  have 
a  flaw  the  other  will  hold  the  truss.  All  trusses  should  be 
slightly  bowed  up  at  the  middle  of  the  span. 

Fig.  142  shows  the  construction  of  a  bridge  for  carrying  a 
penstock. 


Suspension  bridges  are  often  used  to  carry  penstocks  or  heavy 
transmission  lines  across  valleys.  Referring  to  Fig.  143, 
A  B  is  called  the  chord;  A  G  and  B  F  the  backstays,  and  C  E 
the  deflection.  For  all  practical  purposes  the  curve  A  E  B 
may  be  called  a  parabola  in  which  case, 


2C  E 


sm  a    = 


V(2CE)2+(A  B/2)2 


Or  if  one  wishes  to  get  this  angle  from  the  drawing,  lay  off 
O  E  =  to  C  E  and  connect  O  B.  Then  with  the  protractor 
get  the  angle  A  B  O. 

Stress  on  ail  the  suspension  cables  at  A  or  B  equals  one-half 
the  entire  suspended  weight  of  clear  span  and  its  load  divided 


HYDRAULIC  CONSTRUCTION.  169 

by  sin  a.  The  stress  on  the  backstays  will  be  equal  to  that 
on  the  main  cables  if  angle  C  B  O  =  H  B  F,  and  the  stress 
on  the  pier  will  be  vertical  and  equal  to  the  entire  suspended 
weight  of  the  clear  span  and  its  load.  For  this  reason  every 
effort  should  be  made  to  so  locate  the  anchorage  of  the 
backstays  that  the  angle  C  B  O  =  H  B  F. 

In  case  these  angles  are  not  equal,  as  in  Fig.  144,  to  get  the 
stress  and  its  direction  on  the  tower  lay  off  to  scale  on  B  F 
and  O  B  the  stress  on  the  main  cables  as  B  m  and  B  n. 
Then  complete  the  parallelogram  of  forces  B  m  P  n.  Then 
B  p  will  represent  the  magnitude  and  direction  of  the  stress  on 
the  tower.  The  deflection  may  be  from  one-tenth  to  one- 
fifteenth  of  the  span. 

One  of  the  greatest  dangers  to  suspension  bridges  is  the 
effect  of  the  wind,  causing  undulations.  In  the  case  of  a 


FIG.  144. 

bridge  carrying  a  penstock  this  would  result  in  causing  leaks. 
To  guard  against  this  cables  are  used  to  guy  the  span  in  both 
the  horizontal  and  vertical  planes. 

COFFER  DAMS. 

More  money  has  been  needlessly  wasted  on  coffer  dams  than 
upon  almost  any  other  one  structural  detail.  Coffer  damming 
comes  entirely  under  the  cost  of  building,  and  the  contractor 
is  tempted  to  either  build  too  cheaply  or  too  expensively,  de- 
pending a  good  deal  on  the  size  of  the  bond. 

Coffer  dams  may  be  divided  into  classes: 

(1)  Sand  bag;  (2)  Horse;  (3)  Bridge;  (4)  Pile. 

Case  (1).  In  many  instances  the  sand  bag  seems  to  be  the 
only  suitable  means  and  it  is  always  a  costly  one.  Great  care 
must  be  exercised  in  selecting  the  sacks.  Feed,  bone,  meal, 


170 


HYDROELECTRIC  PLANTS. 


etc.,  sacks  unless  perfectly  clean,  will  soon  decay  and  cause 
trouble.  It  pays  to  get  good  sacks.  An  8-ounce,  48-inch 
burlap  sack  is  a  good  size.  The  sacks  should  be  filled  only 
about  three-fourths  full,  so  that  they  may  be  well  packed 
into  the  recesses.  It  takes  about  75  48-inch  burlap  sacks  to 
make  a  row  (when  laid  side  by  side),  100  feet  long.  When  tied, 
such  a  sack  is  about  30  inches  long. 

In  building  a  coffer  dam  to  hold  a  head  of  water,  the  dimen- 


FIG.  145. 

sions  must  be  figured  out  to  resist  that  head  The  base  must 
be  broad  and  the  sacks  laid  with  all  possible  care.  Of  course, 
it  often  occurs  that  the  sacks  must  be  dumped  in  without 
regard  to  packing  or  breaking  joints,  in  which  case  a  broader 
base  is  required.  A  good  rule  to  go  by  is  to  use  two  sacks 
end  to  end  for  the  top  row  and  widen  out  half  the  length  of  a 
sack  on  each  side,  with  each  tier  of  sacks.  This  will  give  sum- 


FIG.  146. 

cient  base  for  all  ordinary  purposes.  On  sand  bottoms  it  is 
usually  necessary  to  pave  the  bottom  with  sacks  as  in  Fig.  145, 
so  that  the  water  falling  oVer  the  dam  before  completion  will 
not  undermine  the  coffer. 

When  the  dam  is  to  be  water-tight,  a  fill  of  earth  or  sand 
will  have  to  be  made  on  the  up  stream  side. 

It  is  sometimes  quite  difficult  to  make  a  sand  bag  stick,  on 
account  of  the  current,  especially  when  closing  up  the  dam. 


HYDRAULIC  CONSTRUCTION.  171 

The  author  was  once  called  upcn  to  build  a  coffer  dam  on  a 
sand  bottom  where  the  current  had  a  velocity  of  about  500  feet 
per  minute.  At  first  six  or  seven,  sand  bags  were  tied  together 
and  thrown  in,  but  the  current  immediately  swept  them  out, 
Finally  the  method  shown  in  Fig.  146  was  adopted.  A  heavy 
rope  was  let  down  to  the  dam  with  seven  sacks  tied  to  it.  The 
current  kept  these  suspended  in  mid-water.  Then  another 
rope  was  let  down  with  seven  sacks  tied  to  it.  These  weighted 
the  first  seven  down  to  bottom  fairly  well,  but  a  third  rope  and 
cluster  of  sacks  was  necessary  to  hold  them  securely.  Now 
the  rope  to  which  the  first  seven  sacks  were  tied  was  cut  loose 
and  used,  for  seven  more  sacks.  In  this  way  the  dam  was 
successfully  built. 

Sand  bags  should  always  be  sewed  as  in  Fig.  147,  thus  forming 


FIG.  147. 

"  ears  "  by  which  they  may  be  handled.  It  is  also  a  better 
shape  for  use  in  the  dam. 

For  estimating  the  number  of  sacks  necessary  to  build  a  coffer 
dam,  assume  that  each  sack  occupies  1J  cubic  feet  of  space  and 
then  add  at  least  ten  per  cent,  for  lost  sacks. 

The  sacks  should  not  be  filled  until  ready  to  place  under 
water  as  they  quickly  decay  if  left  in  the  air  and  moisture. 

According  to  the  author's  experience,  a  coffer  dam  entirely 
of  sand  bags  is  the  most  expensive  and  requires  the  longest 
time  to  build. 

Case  (2).  The  horse  coffer  dam  is  the  invention  of  E.  R. 
Beardsley,  and  in  the  author's  experience  with  hundreds  of 
coffer  dams,  it  has  always  proved  to  be  the  cheapest,  surest 
and  most  quickly  built.  The  method  of  construction  is  as 
follows: 


172 


HYDROELECTRIC  PLANTS. 


A  strong  horse  a  (Fig.  148)  is  built  of  logs  or  squared  timber. 
(For  small  dams  only  two  legs  are  required,  but  for  heavy  work 
four  will  be  necessary,  as  shown  in  Fig.  148.)  If  the  bottom 
is  of  sand,  a  plank,  b,  is  fastened  under  the  legs  as  shown, 
but  where  the  bottom  is  hard,  simply  the  braces,  e,  which  are 
made  of  boards,  one  inch  by  six  inches,  are  spiked  along  the 
sides.  The  legs  are  mortised  into  the  log  and  stand  at  right 
angles  to  it. 

Across  the  horses  are  placed  stringers,  c,  and  on  these  are 
laid  the  poles,  d.  In  placing  the  poles  care  must  be  exercised 
(especially  with  sand  bottoms)  to  avoid  concentrating  the 
current  at  any  one  point.  Begin  at  the  ends  and  work  toward 
the  middle,  placing  the  poles  a  slight  distance  apart,  and  after- 
wards filling  up  the  spaces  left.  Place  the  small  end  of  the 


FIG.  148. — Horse  coffer  dam. 

pole  up  stream.  Brush  are  next  placed  on  the  poles,  the  green 
bushy  ends  being  placed  well  up  stream.  When  the  brush  is  thickly 
and  evenly  distributed  entirely  across  the  dam,  the  ends  of 
the  dam  are  made  safe  by  using  plenty  of  hay,  cane,  corn  stalks, 
etc.,  and  earth. 

The  bottom  or  up  stream  edge  of  the  dam  is  next  made 
secure.  If  the  ends  and  bottom  are  not  made  safe,  all  the 
work  will  be  lost,  and  having  made  them  safe  it  is  then  an 
easy  matter  to  complete  the  job.  On  sand  bottoms  it  is  neces- 
sary to  pave  the  bottom  with  sand  bags  before  the  coffer  dam 
is  commenced.  The  horses  are  usually  placed  about  ten  feet 
apart.  Such  a  dam  is  comparatively  safe  from  floods  and  can 


HYDRAULIC  CONSTRUCTION.  173 

pass  water  over  the  crest.  In  fact,  it  is  almost  impossible  to 
wash  out  such  a  dam.  The  author  built  a  dam  like  this  on 
the  Elkhorn  River,  Nebraska,  where  the  bottom  was  of  the 
worst  possible  sand,  the  current  had  a  velocity  of  over  400  feet 
per  minute,  and  the  water  nine  feet  deep.  The  dam  was  60 
feet  long  and  cost  as  follows: 

Poles $  8.00 

Cutting  Poles 7 . 00 

Cutting  Brush 6.00 

Six  Horses 9.00 

Filling  Sand  Bags 150.00 

2000  Burlap  Sacks 100.00 


$280.00* 
Where  the  bottom  will  permit,  plank  may  be  used  part  way 


-Bridge 


FIG.  149.  • 

in  place  of  the  poles  and  brush.  It  often  happens  that  planks, 
can  be  used  to  build  part  way  out  from  the  ends  and  then 
poles  and  brush  to  close  up  with. 

Case  (3).  It  sometimes  occurs  that  the  current  is  so  swift 
and  the  water  so  deep  that  the  horse  dam  is  impracticable. 
In  such  cases  a  truss  bridge  may  often  be  used.  Figs.  149 
and  150  illustrate  this  method.  Piers  must  first  be  sunk  at 
proper  intervals,  say  40  feet,  and  a  truss  bridge  built  upon  them. 
With  the  truss  as  a  foundation  the  dam  is  built  the  same  as  the 
horse  dam.  In  a  coffer  dam  built  as  shown  in  Fig.  149,  the 
water  was  16  feet  deep  and  the  sand  bottom  was  all  filled  with 
bark  from  saw  logs  which  had  accumulated  for  years. 

Fig.  150  shows  a  three  truss  bridge  floating  on  the  water 
above  a  dam  in  which  there  was  a  break  40  feet  long  and  eight 
feet  deep.  This  truss  was  floated  across  the  break  and  success- 
fully closed  it,  brush  and  gravel  being  used  to  stop  all  leakage.. 

*This  is  $4,66  per  foot  and  should  be  the  maximum  cost.  Small  dams 
on  gravel  bottom  cost  from  50c  to  $2,00  per  foot. 


174 


HYDROELECTRIC  PLANTS. 


Case  (4).  The  coffer  dam  commonly  used  by  engineers  is 
shown  in  Fig.  151.  Sheet  piling  a  is  driven  in  two  rows  the 
distance  between  the  rows  being  about  three-fou'rths  the  depth 
of  the  water.  The  range  piles  b  are  driven  first  and  the  string- 


FIG.  130. — Bridge  built  to  stop  break  in  dam. 

ers,  e,  placed  for  guides  to  the  sheet  piling.  Sand  makes  the 
best  filling  as  any  leak  immediately  makes  its  location  known. 
Clay  puddle  is  often  used.  The.  bottom  of  the  coffer  should 


FIG.  151. 

be  free  from  all  loose  stone   and  gravel,  else  there    is  apt  to  be 
leakage  at  that  point. 

This  type  of  coffer  dam,  when  properly  built,  will  cost  from 
$5.00  to  $10.00  per  linear  foot.  It  is  a  difficult  dam  to  build 
in  swift  water  and  is  not  suited  to  sand  bottoms.  However 
for  certain  conditions  and  places  it  is  a  good  type. 


H  YDRA  ULIC  CONSTR  UCT1ON. 


175 


For  rock  bottoms  the  plan  shown  in  Fig.  152  may  be  used 
either  for  a  caisson  or  for  a  coffer  dam.  The  stringers,  a,  are 
bolted  together  with  the  plank,  6,  placed  at  each  bolt.  These 
planks  are  given  a  taper  and  the  widest  end  is  placed  down. 
Slots  are  made  where  the  bolts  come  so  that  the  plank  can  be 
driven.  The  skeleton  may  then  be  floated  into  position  and 
the  plank,  d,  driven.  In  this  way  a  tight  fit  may  be  made 
with  the  bottom.  The  fill  is  now  made  of  sand  or  clay  puddle. 

The  planks  c  are  bolted  to  the  frame  to  hold  the  skeleton  in 
position  while  being  floated  in  place.  They  also  hold  it  off 


•& 


a 


FIG.  152. 

of  the  bottom  while  the  plank  are  being   driven.      When  used 
as  a  caisson  the  fill  is  made  around  the  outside  as  in  dotted  line. 

CAISSONS. 

Where  it  is  necessary  to  excavate  below  water  a  caisson  is 
used  to  keep  out  the  water.  The  building  of  wheel  pits  almost 
invariably  makes  this  necessary.  For  small  areas  and  shallow 
depths  a  common  earthen  coffer  dam  as  shown  in  Fig.  153  is 
sufficient,  but  for  depths  of  three  feet  or  more  and  when  the 
width  is  not  more  than  18  or  20  feet  it  will  pay  to  build  a 
timber  caisson  as  in  Fig.  154. 


176 


HYDROELECTRIC  PLANTS. 


The  sheeting  should  be  edged  and  given  a  slant  as  shown 
in  Fig.  154  so  as  to  utilize  the  pressure  of  the  water  and  soil. 
If  the  sides  were  made  parallel  the  pressure  at  the  bottom  would 
tend  to  spring  the  caisson  as  shown  in  Fig.  155,  and  in  this 
form  the  water  and  loose  earth  on  the  outside  would  tend  to 
force  it  out.  If,  on  the  other  hand,  the  caisson  has  the  form 


Fig.  153. 

shown  ~n  Fig.  156,  the  water  and  earth  act  as  shown  to  hold 
it  in  place  and  much  less  trouble  will  be  experienced  in  keeping 
it  tight. 

For  excavations  of  large  area  the  author  has  designed  a 
caisson  which  possesses  some  good  features.  Fig.  157  shows 
an  end  view  and  plan.  At  12  foot  intervals  bridge  trusses 


FIG.  154. 

are  placed  across  the  caisson.  The  only  limit  to  the  width 
is  the  limit  to  the  length  of  a  bridge  truss.  Braced  against 
the  top  chord  of  the  truss  is  a  6x6  or  8x8  strutt,  A,  which  rests 
on  the  stringer,  D ;  on  the  under  side  of  this  strutt  is  spiked  or 
bolted  a  cleat  which  receives  the  pressure  of  the  stringer.  At 
F  cleats  are  also  bolted  to  the  lower  chord.  The  stringers 


HYDRAULIC  CONSTRUCTION  177 

D  and  G  are  bolted  to  every  fourth  or  sixth  plank,  slots  being 
made  in  the  plank  to  allow  driving.  At  C  a  platform  is  laid 
loosely  for  a  wheeling  platform  (when  wheelbarrows  are  used), 
and  there  should  be  sufficient  head  room  between  the  truss 
chords  to  permit  a  workman  to  walk  along  with  a  load. 

In  most  soils  large  weights  of  rock  or  timber  will  have  to  be 
piled  on  top  of  the  trusses  to  cause  the  caisson  to  settle,  and  in 
this  case  the  trusses  will  have  to  be  designed  to  sustain  quite 
a  load.  The  pump  is  mounted  on  one  corner  of  the  caisson. 


All  the  timber  can  afterwards  be  used  for  matting  or  concrete 
forms. 

In  the  case  of  a  caisson  of  this  design,  80  feet  long,  40  feet 
wide,  and  8  feet  deep,  it  tQok  12  men  eight  days  to  construct 
and  install  it.  This  does  not  include  excavations. 

With  this  caisson  any  depth  may  he  attained  through  any 
soil.  Nothing  is  fn  the  way  of  the  warlkmen  and  nothing 


FIG.  156. 

to  be  moved  from  the  time  the  sinking  commences  until  it  is 
completed.  A  mat  may  be  laid  all  over  the  bottom  without 
moving  a  pile  or  a  timber. 

Sometimes  the  concrete  walls  are  laid  directly  against  the 
sheeting,  it  forming  one  side  of  the  form,  so  as  to  avoid  leaving 
cavities  or  loose  earth  around  the  outside  of  the  wall. 

A  method  usually  adopted  by  engineers  is  shown  in  Fig.  158. 
This  is  an  end  view  and  shows  the  soil  before  excavation  is 
started.  Round  piling  is  driven  at  equal  intervals  lengthwise 


178 


HYDROELECTRIC  PLANTS. 


and  crosswise  and  about  14  feet  apart.  The  object  of  these 
piles  is  to  hold  up  the  braces  a  which  resist  the  inward  pressure 
of  the  water.  Tight  sheet  piling  b  is  driven  so  as  to  enclose 
the  excavation.  The  workmen  excavate  the  soil  around  among 
the  piles,  and  as  the  level  is  lowered  more  braces  are  placed 
as  at  c.  When  the  desired  depth  D  E  is  reached  the  bottom 


FIG.  157. 

is  concreted  around  the  piling  and  the  walls  built  up.  Then 
the  piles  are  cut  off  level  with  the  floor.  This  leaves  a  portion 
of  the  round  pile  supporting  the  floor  and  usually  many  other 
piles  are  driven  before  concreting  so  that  the  foundation  is 
supportecUon  piling  ancj  the  weight  taken  off  of  the  earth  under- 


FIG.  158. 

neath.  This  is  a  very  bad  thing  to  do  as  the  earth  is  sure  to 
settle  and  a  leak  will  spring  between  the  conrete  and  the  earth. 
The  great  Soo  plant  was  threatened  with  destruction  because 
it  was  thus  built.  Water  got  under  the  power  house  and  washed 
out  a  hole  over  100  feet  wide  and  20  feet  deep. 


HYDRAULIC  CONSTRUCTION.  179 

The  above  caisson  using  bridge  trusses  cost  about  $150  to  build 
and  install,  not  counting  materials  as  they  were  afterwards  used. 
The  same  caisson  if  built  as  in  Fig.  158  would  cost  at  least  $800 
including  the  materials  which  could  not  be  used  again.  Sheet 
piling  is  very  difficult  to  drive  so  that  it  will  be  water-tight 
and  for  caisson  work  it  is  very  essential  that  it  should  be  so. 

Usually  the  caisson  will  have  to  be  protected  from  the  river 
Current  by  a  coffer  dam. 

COSTS. 

The  author  has  found  that  blue  clay  excavation  inside 
caissons  and  where  the  clay  is  too  hard  to  shovel  will  cost 
about  $1.50  per  cubic  yard,  when  wheeled  up  an  incline  to 
an  elevation  of  from  15  feet  to  25  feet.  This  is  the  average 
cost  of  all  the  clay  from  water's  surface  to  a  depth  of  nine  to  12 
feet  below,  labor  at  $1.75  per  day.  It  does  not  include  cost  of 
caisson.  When  taken  from  the  caisson  in  skipps  the  cost  is 
half  that  given  above. 

Sand,  clay  and  gravel,  mixed,  taken  from  a  caisson  1\  feet 
deep  and  not  deposited  higher  than  the  top  of  the  caisson 
costs,  $1.25  per  cubic  yard  to  excavate  by  pick  and  shovel 
and  take  out  by  barrows. 

Gravel  and  quicksand  taken  from  a  caisson  five  feet  deep 
cost  65  cents  per  cubic  yard. 

The  total  cost  of  sinking  a  caisson  36  feet  wide  and  80  feet 
long  to  a  depth  of  nine  feet  in  hard  clay  and  laying  a  mat  con- 
sisting of  two  layers  of  plank  on  sills,  over  the  entire  area, 
was  $1556.  Another  caisson  24  feet  wide,  34  feet  long,  and  7J 
feet  deep  cost  $250  to  sink  in  gravel  and  clay.  Another  24  feet 
by  18  feet  by  six  feet  cost  $200  to  sink  in  gravel  and  silt.  An- 
other 100  feet  by  40  feet  by  14  feet  sunk  in  gravel,  sand  and 
clay  cost  $2200,  a  skipp  being  used  to  elevate  the  materials  to 
the  top  of  a  25-foot  bank.  The  two  largest  caissons  were  built 
as  in  Fig.  157  and  the  others  as  in  Fig.  154.  The  cost  of  operating 
the  pump  and  all  labor  is  included  in  the  above  costs,  as  well 
as  the  laying  of  the  mat. 

PUMPS. 

The  centrifugal  pump  is  one  of  the  most  useful  pieces  of  ma- 
chinery which  is  used  in  hydraulic  construction  work.  It  can 


180  HYDROELECTRIC  PLANTS. 

be  used  for  many  different  purposes;  is  reliable,  is  simple  in 
construction  and  will  stand  a  lot  of  rough  usage. 

It  is  often  employed  in  dredging  work  and  will  remove  all 
sorts  of  soil,  stone,  etc.,  without  being  injured  to  any  great 
degree.  Some  pumps  are  lined  with  steel  to  better  resist  the 
action  of  sand  and  grit.  The  Morris  Machine  Works  recently 
patented  a  pump  which  has  a  removable  and  adjustable  lining. 
The  pump  is  made  in  sections  and  is  particularly  suited  to  moun- 
tain work  where  mule  transportation  is  necessary. 

Up  to  a  few  years  ago  centrifugal  pumps  were  recommended 
for  low  heads  only,  but  the  new  designs  of  multiple  stage  pumps 
driven  at  a  high  speed  by  electric  motors  or  steam  turbines 
can  compete  with  any  high  head  reciprocating  pump  on  the 
market  to-day. 

A  centrifugal  pump  is  a  peculiar  piece  of  apparatus  and  does 
not  behave  like  an  electric  generator  as  many  engineers  are 
wont  to  assume.  In  ordering  a  generator  it  is  always  good 
policy  to  get  a  little  larger  machine  than  is  needed  for  the 
average  load,  but  this  is  not  so  with  the  centrifugal  pump. 
Always  give  the  builder  the  exact  condition  under  which  the 
pump  is  to  work. 

It  very  often  happens  that  the  purchaser  orders  a  pump  of 
larger  capacity  or  higher  head  than  he  needs  so  as  to  be  on 
the  safe  side  as  he  puts  it,  and  is  surprised  to  find  that  his 
motor  or  engine  takes  an  astonishing  amount  of  power  and 
perhaps  won't  drive  it  at  all.  The  formula  for  the  power 
necessray  to  drive  the  pump  is 

HQ62.5  . 
,-33000-'  m  h°rse  P°Wer' 

wherein  H  is  the  head  in  feet;  Q  the  volume  discharged  in 
cubic  feet  per  minute  and  rj  the  efficiency. 

The  efficiency  of  the  pump  is  best  when  the  water  passes 
through  it  at  the  velocity  calculated  by  the  builder,  but  for 
any  other  velocity  above  or  below  this  the  efficiency  will  fall 
off  roughly  as  shown  in  Fig.  159. 

If  the  static  head  is  constant  and  it  is  desired  to  vary  Q,  the 
effective  head  must  be  varied  either  by  varying  the  speed  or 
by  throttling  the  exhaust.  Throttling  causes  a  waste  in  head 
and  reduces  the  efficiency,  while  reduction  in  speed  reduces 


H YDRA  ULIC  CONSTR  UCT1ON. 


181 


the  efficiency  of  the  steam  engine  and  is  impossible  with  the 
constant  speed  a  c  motor.  Referring  to  the  curve  it  is  seen 
that  horse-power  is  practically  constant  for  loads  below  normal, 
so  that  the  efficiency  is  very  poor  at  low  loads.  The  horse-power 
W ',  under  these  conditions,  is  expressed  by 

_Q  _  #.62.5 

?T  =        '  33000 

From  this  equation  it  is  seen  that  Q  and  17  decrease  together, 
therefore  the  reduction  in  power  is  slight. 

On  the  other  hand  suppose  that  a  pump  designed  for  a  20-foot 
pressure  head  is  used  to  dredge  under  a  2-foot  pressure  head, 
and  that  it  is  directly  connected  to  a  high-speed  steam  engine 
or  an  electric  motor.  The  reduction  in  head  will  cause  an 


FIG.  159. 

enormous  increase  in  Q,  which  will  clog  the  pump  and  if  driven 
by  an  engine  bring  the  engine  nearly  to  standstill;  if  driven  by 
a  motor  will  blow  the  fuse  on  a  continuous  current  motor,  and 
cause  an  induction  motor  to  run  over  the  breakdown  point  and 
stop.  For  all-round  work  a  variable  speed  motor,  which  is 
provided  with  a  compensating  winding  or  inter  poles,  should 
be  used.  These  motors  can  be  efficiently  varied  over  a  large 
speed  range  and  at  the  same  time  give  a  constant  output. 

Another  disadvantage  in  having  too  large  a  pump  is  that  it 
cannot  be  run  continuously;  for  instance,  in  pumping  out  a 
caisson  it  will  have  to  be  continually  started  and  stopped,  and 
may  cause  trouble  due  to  the  priming.  A  globe  valve  placed  in 
the  discharge  does  away  with  all  priming  trouble. 


182 


HYDROELECTRIC  PLANTS. 


In  important  work  there  should  always  be  two  pumps,  so  as 
to  have  one  in  reserve.  Tables  of  speeds  and  powers  for  different 
heads  are  obtainable  from  any  of  the  makers. 


FIG.  160. 

A  velocity  of  10  feet  per  second  should  not  be  exceeded  in  the 
suction  or  delivery  pipe.     The  suction  pipe  should  be  perfectly 


FIG.  161. — Centrifugal  pump. 

air-tight.     A  gate  valve  should  be  located  near  the  pump  in 
the  delivery  pipe.     A  coarse  screen  should  encase  the  lower  end 


HYDRAULIC  CONSTRUCTION.  183 

of  the  suction  pipe  to  prevent  stones  entering  and  getting  under 
the  valves. 

Before  starting,  the  pump  must  be  filled  with  water.  In  order 
to  make  this  possible  the  pump  must  be  supplied  with  some  kind 
of  valves  in  the  suction  or  delivery  pipes.  If  the  valve  is  in  the 
discharge  the  air  must  be  exhausted  and  the  water  from  the 
suction  allowed  to  fill  the  pump.  The  air  can  be  exhausted 
with  a  hand  air  pump  or  with  an  ejector  operated  by  steam, 
compressed  air  or  water  under  high  pressure.  On  the  other 
hand  if  the  valve  is  in  the  suction  the  pump  must  be  filled  with 
water  from  above.  This  may  be  done  with  pails,  with  an 
ejector  or  by  allowing  water  to  run  in  from  a  barrel  or  tank. 
Figs.  160  and  161  show  the  connections  for  an  ejector  used 
respectively  with  a  valve  in  the  discharge  and  suction  line. 

Pumps  supplied  with  flap  or  foot-valves  will  hold  their  prime 
for  quite  a  while  when  not  in  use,  at  least  long  enough  to  premit 
the  use  of  a  pump  in  intermittent  work,  such  as  filling  a  tank 
controlled  by  a  float.  The  delivery  valve  should  not  be  opened 
until  the  pump  is  up  to  speed. 

HYDRAULIC  RAM. 

Another  simple  piece  of  apparatus  which  is  often  used  to  raise 
water  is  the  hydraulic  ram. 

The  simple  and  effective  operation  of  this  machine,  and  its 
great  durability,  render  it  a  most  useful  and  valuable  apparatus 
for  elevating  water,  and  conveying  it  to  almost  any  desired  dis- 
tance. 

It  is  practicable  where  the  spring  or  brook  is  only  18  inches 
higher  than  the  ram ;  yet  as  the  height  increases,  the  more  power- 
fully the  ram  operates,  and  its  ability  to  force  water  to  a  greater 
elevation  and  distance  is  correspondingly  strengthened.  The 
relative  height  of  the  spring  or  source  of  supply  above  the  ram, 
and  the  elevation  to  which  it  is  required  to  raise,  determine  the 
relative  proportion  between  the  water  raised  and  wasted — the 
quantity  raised  varying  according  to  the  height  it  is  conveyed 
with  a  given  fall ;  also  the  distance  the  water  has  to  be  conducted, 
and  the  consequent  length  of  pipes,  have  some  influence  on  the 
quantity  delivered  at  the  point  of  discharge,  as  the  more  ex- 
tended the  pipes  through  which  the  water  has  to  be  forced  by 
the  ram,  the  more  friction  there  is  to  overcome  by  additional 


184  HYDROELECTRIC  PLANTS. 

effort  on  the  part  of  the  machine;  notwithstanding  rams  are 
frequently  and  successfully  employed  for  driving  water  a  distance 
of  100  to  200  rods,  to  an  altitude  of  100  to  200  feet  dbove  the 
ram,  and  severer  trials  than  this  even,  testify  to  the  indispen- 
sibilty  of  this  almost  automatic  device.  A  fall  of  10  feet  from 
the  brook  or  spring  to  the  ram  is  abundantly  sufficient  to  raise 
water  to  any  point  less  than  150  feet  above  the  location  of  the 
machine,  while  the  same  amount  of  fall  will  also  raise  water 
considerably  higher,  though  the  quantity  of  water  will  be  pro- 
portionately diminished  as  the  height  and  distance  increase. 
When  the  requisite  quantity  of  water  is  forthcoming  from  the 
ram,  operating  under  a  certain  fall,  it  is  not  judicious  to  give 
it  more  fall,  for  by  so  doing  the  strain  on  the  machine  is  meas- 
urably augmented,  those  parts  doing  the  labor  are  overtaxed, 
and  the  durability  of  the  apparatus  impaired  and  lessened. 

For  ordinary  purposes  it  is  sufficient  to  say,  that  in  Conveying 
water,  say  50  to  60  rods,  it  may  be  safely  calculated  that  from 
one-tenth  to  one-fourteenth  of  the  water  can  be  raised  and  dis- 
charged at  an  elevation  ten  times  as  high  as  the  fall  or  one- 
seventh  part  of  the  water  can  be  raised  and  discharged,  say  five 
times  as  high  as  the  fall  applied,  and  so  in  like  proportion  as  the 
fall  or  height  is  varied.  Thus  with  a  fall  of  five  feei  of  every 
seven  gallons  drawn  from  the  fountain,  one  may  be  raised 
25  feet  or,  half  a  gallon,  50  feet.  Or,  with  10  feet  fall,  one  gallon 
of  every  14  may  be  raised  to  a  height  of  100  feet,  and  bo  in  like 
proportion  as  the  fall  or  height  is  varied.  (See  general  rule.) 

Where  the  water  is  to  be  forced  to  any  great  distance,  say 
more  than  75  rods,  it  is  preferable  to  use  a  discharge  pipe  of 
larger  caliber  than  named  in  the  table. 

Several  rams  can  be  set  so  as  to  play  into  one  discharge  pipe — 
each  ram  having  a  separate  drive  pipe  applied  from  the  spring 
to  the  ram. 

The  size  of  the  pipe  may  be  varied  in  proportion  to  the  dis- 
tance the  water  is  to  be  conveyed,  as  the  greater  the  distance 
the  larger  the  pipe  in  proportion  to  the  size  of  the  machine. 
This,  however,  applies  only  to  the  discharge  pipe. 

Turns  in  either  drive  or  discharge  pipe  should  be  avoided 
if  possible.  When  it  is  impossible  to  set  the  ram  without 
having  elbows  in  the  pipes,  make  the  elbows  as  large  as  may 
be  so  as  to  place  as  little  obstruction  to  the  free  and  easy  flow 
of  the  water  as  is  practicable. 


H  YDRA  UL1C  CONSTR  UCTION. 


185 


These  machines  are  made  of  iron  and  brass.  The  valve 
stems  are  made  of  bronze,  which  has  more  durable  and  lasting 
qualities  than  any  other  composition.  The  annexed  table 
exhibits  the  capacity,  size,  price,  etc. 

GENERAL    RULE. 

Multiply  the  number  of  gallons  furnished  by  the  spring, 
per  minute,  by  936;  multiply  this  product  by  the  height 
of  the  spring  (in  feet)  above  ram;  then  divide  by  the 
height  (in  feet)  between  ram  and  point  of  delivery.  The  result 
will  be  the  number  of  gallons  delivered  per  day  of  24  hours. 

The  following  table  gives  the  capacity  of  the  several  sizes  of 
Rumsey  &  Company  rams  and  the  dimensions  of  the  pipes  to 
be  used  in  connection  with  same. 


Table  XXXV. 


Size 
of 
Ram. 

Minimum 
Quantity  of 
Water  Required 
to  Operate 
Ram. 

Length 
of  Drive 
Pipe. 
Feet. 

Calibre  oi  Pipes. 

Price. 

Drive. 

Dis- 
charge. 

Gals,  per  Min. 

•    Inches. 

Inches. 

No.  2 

2 

Five  to  six  times 

| 

1 

$  9.00 

No.  3 

4 

height  of  the  sup- 

1 

i 

11.00 

No.  4 

8 

ply. 

14 

i 

14.00 

No.  5 

14 

2 

i 

22.00 

No.  6 

25 

2* 

U 

40.00 

No.  7 

60 

4 

2 

75.00 

No.  8 

120 

6 

2J 

125.00 

EMBANKMENTS. 

Embankments  frequently  play  an  important  part  in  hydraulic 
work.  It  stands  to  reason  that  the  embankment  should  be  as  per- 
manent as  any  other  part  of  the  work,  yet  they  are  too  often 
scrimped  and  built  by  guess. 

Too  much  care  can  not  be  taken  in  thoroughly  cleaning  the 
ground  where  the  embankment  is  to  stand,  of  all  grass  and  loose 
stone,  etc.  It  must  then  be  well  plowed.  To  neglect  this  will  in- 
sure a  seepy  and  dangerous  embankment.  Avoid  making  a  fill  of 
earth  having  a  large  proportion  of  stone.  The  earth  washes 
out,  leaving  a  leaky  embankment. 


180  HYDROELECTRIC  PLANTS. 

Clay  or  sand  are  the  best  materials  for  this  work.  Sand 
has  the  great  advantage  of  being  rat  proof.  The  musk  rat  is  a 
constant  menace  to  all  earth  embankments.  They  start  digging 
two  or  three  feet  under  water,  taking  advantage  of  every  root 
or  stone  to  support  the  roofs  of  their  burrow,  and  when  into 
the  embankment  a  few  feet,  dig  upward  to  get  above  the  water 
for  their  nest.  They  then  continue  digging  downward  till  they 
emerge  on  the  down  stream  edge  of  the  embankment  and  just 
under  water. 

Their  work  remains  concealed  until  the  floods  come  and  then 
there  is  a  call  for  quick  work.  A  purely  sand  embankment, 
while  demanding  flatter  slopes,  is  safe  against  rats  because  the 
sand  falls  in  as  fest  as  they  dig  and  thus  stops  them.  Again  any 
seepage  makes  its  location  known  at  once  while  in  a  clayey 
soil  a  large  cavity  may  be  washed  out  without  any  warning. 


FIG.  162. 

A  puddle  wall  in  the  center  (Fig.  162)  is  often  used  to  prevent 
seepage,  but  this  is  a  bad  design  as  it  renders  useless  all  that  part 
of  the  embankment  on  the  up-stream  side  of  the  puddle.  All 
the  expense  in  making  the  embankment  water  tight  should  be 
spent  on  the  up-stream  side.  Fig.  163  shows  the  proper  sec- 
tion. The  clay,  when  used,  is  put  on  after  the  fill  is  all  in.  It 
should  be  thoroughly  damped  and  tamped, 

Where  the  materials  can  be  selected,  the  most  impervious  are 
put  on  the  up-stream  side  and  the  coarser  and  more  sandy  on 
the  down  stream  side  of  the  embankment. 

At  the  top  the  width  should  be  at  least  12  feet,  which  allows 
for  a  wagon  road  and  gives  about  the  right  proportions.  The 
slope  of  the  sides  should  be  determined  as  described  in  page 
188.  A  slope  of  two  to  one  for  the  down-stream  side  and  three 
to  one  for  the  up-stream  is  a  common  section. 


HYDRAULIC  CONSTRUCTION.  187 

The  depredations  of  the  rat  may  be  guarded  against  by  prop- 
erly rip-rapping.  It  will  not  serve  the  purpose  to  merely  throw 
in  a  large  quantity  of  rock,  as  to  do  so  makes  the  best  possible 
refuge  for  the  pest.  A  mink  or  musk  rat  will  find  a  dozen  fine 
passages  through  such  riprap,  and  the  mass  of  loose  stone 
serves  to  hide  the  burrow. 

A  splendid  riprap,  and  one  which  is  not  at  all  expensive,  is 
to  pave  the  up-stream  slope  with  a  4-inch  layer  of  concrete  in 
which  wire  netting  is  imbedded.  If  rocks  are  used  they  should 
be  laid  with  great  care  so  that  while  they  leave  no  holes  that  one 
could  get  one's  hand  through,  they  at  the  same  time  do  not 
afford  a  hiding  place. 

In  a  well  designed  embankment  the  line  of  seepage  should 
strike  within  the  base  as  in  Fig.  163.  There  is  no  way  of  pre- 
determining the  line  of  seepage  except  by  building  an  experi- 
mental embankment. 


FIG.  163. 

CANALS. 

In  selecting  the  location  for  the  canal,  it  must  be  borne  in 
mind  that  the  longest  way  round  may  be  the  best.  The  cheap- 
est canal  is  one  dug  along  a  hillside  and  in  such  a  way  that  the 
excavation  just  forms  one  bank  as  in  Fig.  164.  This  possesses 
certain  disadvantages,  one  of  which  is  the  danger  of  seepage 
along  the  line  A  B.  However,  if  the  soil  is  well  ploughed  before 
the  fill  is  to  be  made  and  the  fill  thoroughly  packed  by  horses 
or  otherwise  (see  embankments)  there  should  be  no  trouble 
from  this  source. 

A  canal  of  this  sort  is  exposed  to  the  depredations  of  musk- 
rats,  and  should  be  regularly  inspected.  If  there  is  difficulty 
in  getting  the  proper  slope  at  D  E  that  side  may  be  riprapped 
or  sheeted.  Where  the  soil  is  treacherous  as  is  the  case  with 


188 


HYDROELECTRIC  PLANTS. 


certain  clayey  loams,  a  puddled  wall  (see  page  186)  should 
be  built.  One  of  the  most  important  items  in  the  design  of 
an  earth  canal  is  the  selection  of  the  proper  angle  for  the  banks. 
The  angle  at  which  the  earth  will  stand  without  flowing  down 
is  called  the  angle  of  repose,  and  this  angle  must  be  determined 


FIG.  164. 

before  work  is  commenced.  The  only  safe  plan  is  to  take  a 
quantity  of  the  soil  from  the  line  of  the  canal  and  bank  it  up 
in  water.  The  angle  which  the  soil  assumes  under  these  cir- 
cumstances may  safely  be  taken. 

Once  the  author  built  a  long  embankment  out  of  what  ap- 
peare.d  to  be  good  soil  for  the  purpose.     In  dry  embankment 


FIG.   165. 


it  packed  splendidly,  there  being  just  enough  clay  mixed  with 
the  light  loam  to  make  it  stand  up  well  But  when  the  pond 
was  filled  the  embankment  ran  like  oil  and  it  required  the  most 
desperate  all-night  work  to  keep  the  top  a.bo.ve  water.  A  few 
practical  lessons  like  this  teach  the  importance  of  careful  pre- 


H  YDRA  ULIC  CONSTR  UCTION. 


189 


liminary  examination.  No  safe  rule  can  be  given  for  the  angle 
of  repose  and  no  two  engineers  will  agree  on  what  it  is. 

The  section  shown  in  Fig.  165  is  betterthan  Fig.  164  as  the  loose 
earth  excavated  is  above  the  water  line  as  is  the  line  of  greatest 
seepage.  It  is  a  good  plan  to  place  the  edge  a  of  the  fill  a  few 
feet  away  from  the  edge  of  the  canal.  This  space  is  called  the 
berm  and  serves  to  catch  the  sluffings  from  the  fill. 

In  spite  of  the  fact  that  a  lining  reduces  the  area  of  a  canal, 
unless  the  bottom  and  sides  are  uniform  and  smooth,  it  should 
always  be  installed.  If  there  is  plenty  of  room,  a  plain,  un- 
sheeted  canal  can  be  made,  in  earth,  with  good  uniform  bottom 


and  sides  and  having  n  =  .024.  All  large  stone  should  be  re- 
moved and  the  entire  surface  tamped.  But  where  a  hill  rises 
on  one  side,  or  where  a  high  velocity  is  required,  it  often  becomes 
necessary  to  sheet  the  canal. 

A  timber  sheeting  is  good  on  the  bottom,  the  coefficient  n 
being  small  for  planed  plank,  but  where  the  sheeting  is  near 
the  water  line  it  should  be  made  of  more  permanent  material. 
The  sheeting  shown  in  Fig.  166  was  designed  by  the  author 
and  is  a  combination  of  timber  and  reinforced  concrete.  The 
timber  mat  here  shown  consists  of  a  single  platform  of  planed 
planks  two  inches  thick,  nailed  to  timbers  p.aced  across  the 
canal  at  intervals  of  five  or  six  feet.  This  mat  is  held  down 
by  the  weight  of  the  concrete  but  where  the  canal  is  so  wide 
that  the  sills  will  not  reach,  the  mat  will  have  to  be  made  double 
and  filled  with  gravel  (seepage  220).  The  slopes  are  built  of 


190  HYDROELECTRIC  PLANTS. 


concrete  and  are  from  six  inches  to  12  inches  thick,  depending 
on  the  height,  the  buttresses  having  the  same  thickness  when 
wire  reinforcement  is  used.  The  cost  of  such  a  lining  is  not  at 
all  prohibitive.  The  slopes  for  a  canal  six  feet  deep  cost  all 
complete  about  $3.60  per  linear  foot,  of  canal  with  concrete 
at  $6.00,  and  netting  at  three  cents  per  square  foot.  The 
bottom  sheeting  would  require,  for  a  canal  28  feet  at  the  top, 
65  square  feet  of  mat  and  would  cost  two  cents  per  square  foot 
for  laying.  This  would  make  the  entire  sheeting  cost  (lumber  at 
$18.00)  about  $6.00  per  linear  foot  of  canal.  If  the  bottom  is 
also  of  concrete-steel,  as  in  Fig.  167,  the  cost  would  be  about 
$3.00  more  than  the  above.  To  offset  the  cost  of  sheeting,  we 
have  the  decreased  area  of  canal,  making  it  cheaper  to  build. 

Take  two  canals,  one  having  n  =  .01  and  the  other  .03, 
then  the  sheeted  canal  having  the  same  area  and  slope  will 
carry  fully  twice  as  much  water  as  the  rougher  canal. 


FIG.  167. 

To  illustrate  the  saving  in  cross-seotion  by  sheeting  the  fol- 
lowing example  is  given: 

A  canal  having  a  section  like  that  shown  in  Fig  1 67  is  built 
with  a  fall  of  two  feet  per  mile. 

Then 

.000378. 


5280 

The  area  A  =  460  square  feet,  the  wetted  perimeter  P  =  65.4 
and  the  hydraulic  radius  is 

460 

r  =  „_••- r  =  7.1 
65.4 

Taking  C  =  195  (see  page  26), 

v  =  CV7V7~==  195  V77T\/0. 000378 "=  10  feet  per  second, 
and 

Q  =  10X460  =  4600  cubic  feet  per  second. 


H  YDRA  UL1C  CONS  TR  UCT1ON. 


191 


If  the  canal  is  in  earth  and  must  carry  about  the  same  amount 
of  water,  assuming  a  section  shown  in  Fig.  168 

696 

r-"^=S-7 

From  formula,  C  =  73 

v  =  73V8T7   X    V- 000378  =4.17  feet  per  second. 


FIG.  168. 

Q  =  696 X  4.17  =  2900  cubic  feet  per  second,  which  is  some- 
what less  than  the  concrete -lined  canal  will  carry. 

The  fall  in  the  two  canals  is  the  same,  but  the  velocity  head 
(head  necessary  to  set  the  water  in  motion,  v,  at  the  head  of 
canal)  will  be 


H 


102 


64.32      64.32 


=  1 . 56  feet  for  the  first  section,  and 


FIG.  169. 


H 


4.172 
64732 


0 . 38  foot  for  the  second  section. 


Therefore  1 . 29  foot  or  about  fifteen  inches  more  head  would  be 
lost  in  the  case  of  the  canal  with  the  higher  velocity.  However, 
this  fifteen  inches  is  for  the  whole  canal,  no  matter  how  long. 

Figuring  the  excavation  at  12  cents  per  cubic  yard,  the  first 


192  HYDROELECTRIC  PLANTS. 

canal  would  cost  $2  per  foot  to  excavate,  while  the  second 
would  cost  $3.12  per  foot. 

The  reinforced  concrete  section  shown  in  Fig.  167  does  not 
require  embankments  of  any  kind,  and  could  be  built  on  the 
surface  of  the  ground,  thus  under  favorable  conditions  saving 
all  excavation.  Also,  the  sheeted  canal  would  not  be  choked 
with  grass  or  sediment.  Again,  if  the  floor  is  laid  tight,  a 
much  lighter  embankment  would  be  required  if  the  section  is 
as  Fig.  168.  The  bottom  and  slopes  may  be  paved  with  cobble 
stones  or  flags,  and  then  given  a  four-inch  coating  of  con- 
crete, the  proportions  being  about  4  to  1. 

The  banks  may  be  held  by  means  of  masonry  walls  (Fig.  169). 
Unless  the  walls  are  much  heavier  than  usually  built  they  must 
be  provided  with  weep  holes,  so  that  when  the  canal  is  emptied 
the  water  back  of  them  will  not  push  them  in.  These  walls 
should  have  a  good  bottom  when  possible.  If  the  walls  are 
made  of  well-rammed  concrete  and  the  floor  is  tight,  the  weep 
holes  are  not  required,  in  which  case  the  sub-soil  under  the  walls 
should  be  drained.  Masonry  walls  cannot  (in  practice)  be  built 
water-tight.  The  top  thickness  of  these  walls  should  never 
be  less  than  two  feet ;  otherwise  the  frost  will  bulge  them  out 
after  a  few  winters.  Next  to  concrete,  brick  makes  the  most 
efficient  lining. 

TUNNELS. 
ROCK. 

Frequently  penstocks  or  canals  have  to  be  run  through  tunnels, 
as  in  the  case  of  the  Mill  Creek  plant  (page  199,  Penstocks). 
Every  effort  should  be  made  to  thoroughly  determine  the 
character  of  the  materials  to  be  penetrated.  In  many  tunnels 
the  estimated  cost  has  been  greatly  exceeded  on  account  of 
unforseen  difficulties,  such  as  caving  and  movement  of  the  entire 
mountain  above  the  tunnel.  In  selecting  the  section  the  area 
should  be  calculated  with  n  =  .035  and  with  n  --=  .011.  In  the 
first  case  the  tunnel  will  not  have  to  be  lined  and  in  the  second 
it  will.  Then  by  calculating  the  comparative  cost,  the  cheaper 
section  may  be  selected. 

The  drilling  is  usually  done  with  machine  drills,  but  may  be 
done  by  hand,  or  both  may  be  used.  In  long  tunnels  work  is 
begun  at  both  ends  at  the  same  time.  The  number  of  drills 


HYDRAULIC  CONSTRUCTION. 


193 


used  depends  on  the  size  of  the  tunnel.  For  a  tunnel  20  by  30 
feet  three  drills  are  used.  Compressed  air  is  the  best  motive 
power  for  the  drills  where  the  tunnels  are  long,  as  the  exhausted 
air  serves  to  ventilate  the  tunnel.  A  three-inch  pipe  will  be  suffi- 
cient to  supply  the  air  for  six  12-horse -power  drills;  a  24-inch 
pipe  for  four  drills,  and  a  2-inch  pipe  for  two  drills.  The  boiler 


FIG.  170. 

capacity  should  be  about  13  boiler  horse  power  per  drill.  The 
engine  and  compressor  plant  should  be  situated  outside  and  near 
the  tunnel. 

In  excavating  the  tunnel,  it  is  divided  into  two  parts,  one 
called  the  heading  and  the  other  the  bench  (Fig.  170).  The 
heading  is  made  only  sufficiently  high  to  provide  a  head  room 
for  working,  and  is  carried  a  hundred  feet  or  so  ahead  of  the 


FIGS.  171.    172. 

bench.  In  working  the  heading  the  drills  are  mounted  on 
columns  jacked  tightly  between  the  floor  and  roof,  as  shown  in 
Fig.  170.  The  flexible  hose  connecting  the  drill  to  the  air  pipe  is 
attached  to  the  manifold,  to  which  several  hoses  may  be  connected. 
Figs.  171-173  show  how  the  holes  are  drilled.  The  holes  1, 
2,  3,  4,  5,  6,  7,  and  8,  are  called  'center  cut  holes,  and,  as  shown  in 
Fig.  173,  each  pair  meets  on  the  center  line  of  the  tunnel.  The 


194 


HYDROELECTRIC  PLANTS. 


wedged  shaped  mass  a,  6,  c,  (Fig.  173)  is  blasted  out  first  and 
the  operation  is  called  breaking  the  cut.  The  side  round  holes 
9,  10,  11,  12,  etc.,  are  drilled  at  the  same  time  as  the  center  cut 


FIG.  173. 


holes,  and  all  are  loaded.  The  center  cut  holes  are'all  fired  at 
once  and  then  the  side  cut.  The  heading  is  then  enlarged  at 
the  sides  by  drilling  holes  as  shown  in  Fig.  174,  the  holes  being 


vmzz^ 

FIG.  174. 

given  a  slant  back  in  the  direction  of  the  completed  tunnel  of 
about  60  degrees  to  the  center  line. 


FIG.  175. 


After  the  bottom  of  the  heading  has  been  widened  out  to 
the  contour  line  of  the  tunnel  the  holes  a  in  Fig.  175  are  drilled 
about  five  feet  apart  across  the  tunnel.  When  a  sufficient 


HYDRAULIC  CONSTRUCTION.  195 

ledge  has  been  formed  at  5,  more  drills  are  started  drilling 
the  holes  c.  Where  the  drilling  is  perpendicular  to  the  surface 
of  completed  tunnel  as  in  Fig.  174  the  holes  are  drilled  to  the 
contour,  but  where  they  are  parallel  to  the  tunnel's  sides  as 
at  D  and  E,  Fig.  175,  they  are  drilled  to  within  about  a  foot 
so  that  the  explosive  will  not  shatter  the  permanent  walls. 

The  charge  used  must  depend  on  the  particular  rock  and  drill- 
ing. The  center  cut  is  blasted  with  very  strong  dynamite  or 
jovite,  containing  say  from  50  to  80  per  cent,  nitroglycerine. 
For  bench  work  a  40  per  cent,  dynamite  is  good.  The  rock 
should  be  broken  up  sufficiently  to  load  into  barrows  without 
difficulty.  If  jovite  is  used  for  the  explosive  (see  page  158),  two 
pounds  is  used  for  the  bench  and  three  pounds  for  the  center  cut. 

EARTH. 

In  tunneling  through  earth,  especially  if  the  earth  is  full  of 
water,  the  engineer  meets  one  of  the  severest  tests  of  his  capacity. 

A  brief  description  of  the  Went  worth  Street  sewer  tunnel  at 
Cleveland,  O.,  will  give  an  idea  of  the  principle  involved.  This 
tunnel  was  through  wet  earth  and  under  tracks  which  could  not 
be  allowed  to  settle,  so  the  conditions  were  the  most  severe. 
Of  course,  when  the  tunnel  is  small,  fewer  headings  have  to 
be  run  and  often  only  one  is  necessary. 

The  excavation  was  made  in  eight  operations  and  the  masonry 
was  built  in  four  operations.  The  total  excavation  was  21  feet 
high  and  25  feet  wide,  and  was  made  piecemeal  from  both 
sides  and  from  the  top  down.  First  a  heading  seven  feet  high 
and  nine  feet  wide,  with  the  roof  sloping  both  ways,  was  driven 
in  the  haunches  of  the  tunnel  arch  on  each  side  simultaneously. 
Its  position  and  dimensions  are  shown  in  Fig.  176;  it  is  marked 
1-1,  etc.  After  a  convenient  length  of  these  headings  had  been 
driven  benches  about  five  feet  deep,  marked  2-2,  were  excavated 
and  finally  a  second  bench,  3-3,  on  each  side  of  the  center  line, 
was  excavated  to  below  grade.  After  the  headings  1-1  were 
driven  two  12xl2-inch  longitudinal  suspension  timbers  were 
laid  on  top  of  the  bottom  sills  in  each  heading  and  supported 
on  wedges  at  both  ends.  The  sills  were  chained  to  the  longi- 
tudinal timbers,  and  made  snug  with  pairs  of  wedges.  Then, 
bearing  cleats  having  been  nailed  to  the  vertical  posts  above 
the  sills,  the  bench  was  excavated  and  the  timbering  was  sup- 


196 


HYDROELECTRIC  PLANTS. 


If 


rn^^mi 

.-•-;••  it  £',  -8 


HYDRAULIC  CONSTRUCTION.  197 

ported  from  the  longitudinal  timbers  until  the  second  sections 
of  the  vertical  posts  could  be  driven  in  under  the  bottoms  of 
the  first  ones  and  the  side  lagging  and  lower  cross  struts  placed. 
The  second  bench  was  then  taken  out  in  a  similar  manner. 

The  concrete  side  walls  5-5  were  then  built  in,  the  vertical 
timbers  and  lagging  being  left  permanently  in  the  ground  and 
the  cross  struts  being  removed  as  the  concreting  progressed. 
The  upper  center  heading  4  was  through  very  fine  dry  sand  with 
about  18  feet  cover,  and  as  the  face  had  to  be  continually  pro- 
tected by  vertical  transverse  bulkheads,  it  was  excavated  in 
three  parallel  successive  drifts,  as  shown  in  the  plan  and  sec- 
tions. These  drifts  were  started  at  the  highest  part  of  the  tunnel 
and  made  only  three  feet  high  and  three  feet  long,  the  bottom 
sloping  downward  and  backward  and  the  sides  being  retained 
by  poling  boards  and  bulkheads.  The  front  bulkheads  were 
braced  back  against  temporary  horizontal  cross  struts,  and  when 
the  whole  width  of  the  heading  was  excavated  the  drifts  were 
deepened  to  a  point  below  the  tops  of  the  walls  of  sections  1-1 
and  the  permanent  roof  timbers  were  put  in,  supported  by 
inclined  posts  at  the  ends  which  rest  on  the  apexes  of  the  side 
tunnels  and  on  vertical  center  posts. 

Collapsible  timber  centers  for  the  brick  arches  were  made 
in  three  sections  each,  bolted  together  at  the  splices  as  shown 
in  the  elevations,  with  long  tongue  and  groove  joints.  These 
centers  were  set  between  timbers  on  horizontal  longitudinal 
sills  supported  on  the  concrete,  and  jack  screws  were  set  on  top 
of  them  under  the  roof  timbers  and  screwed  up  to  relieve  the 
pressure  on  the  braces  and  allow  them  to  be  removed.  The 
lagging  was  then  laid  as  required  and  the  aich  6-6  completed, 
leaving  the  roof  timbers  permanently  in  place,  The  centering 
was  not  braced  or  secured,  but  was  found  rigid  and  satisfactory. 

Finally  the  dumpling,  7,  was  removed  and  the  concrete  invert 
8  being  laid,  the  tunnel  section  was  completed.  The  sequence 
of  the  different  operations  is  indicated  by  the  numerals  written 
on  t1ie  different  parts  of  the  sections,  which  correspond  in  the 
several  views.  The  material  encountered  was  fine  sandy  clay 
and  loam,  about  half  of  it  being  below  the  ground  water  line. 
The  sides  and  roof  were  sheeted  everywhere  with  2-inch  lagging 
in  3-foot  lengths  and  the  benches  were  taken  out  between 
bulkheads.  The  material,  especially  when  wet,  would  run 


198  HYDROELECTRIC  PLANTS. 

/^  . 

very  easily,  and  large  quantities  of  marsh  hay  were  used  to  pack 
in  behind  the  lagging.  It  was  often  difficult  to  set  the  lagging 
and  sometimes  it  was  blocked  and  wedged  as  much  as  a  foot 
back  from  the  timbers.  Wedging  and  cleats  were  used  very 
freely  and  the  headings  were  advanced  about  three  feet  in  ten 
hours  by  six  miners  in  each  heading.  The  rest  of  the  work 
was  carried  on  at  a  corresponding  rate  and  about  50  men  in  all 
were  employed  in  each  of  two  shifts  in  24  hours. 

The  tunnel  was  driven  through  from  one  end  only  and  mate- 
rials were  handled  in  and  out  of  the  single  shaft  by  a  boom 
derrick.  The  spoil  was  shoveled  from  bench  to  bench  and  then 
taken  to  the  shaft  in  wheelbarrows;  the  concrete  was  mixed 
on  the  surface  of  the  ground  at  the  foot  of  the  railroad  em- 
bankment and  wheeled  to  the  required  place  in  the  tunnel. 
The  bottom  of  the  tunnel  was  graded  about  1:1000  downward 
from  the  shaft,  but  all  the  water  was  removed  by  a  steam 
pump  with  its  suction  in  a  sump  three  feet  deep  in  the  bottom 
of  the  shaft.  The  sewer  was  lined  with  very  hard  tough  vitri- 
fied shale  brick  locked  in  to  the  Flemish  bond  of  the  arch  rings. 
Notwithstanding  the  utmost  care  in  tunneling  the  railroad  tracks 
above  the  tunnel  settled  several  inches  some  days,  and  were 
frequently  raised  and  tamped  with  cinders.  The  16-foot  cir- 
cular section  of  the  outfall  sewer  is  flattened  and  widened  to  a 
50-foot  channel  at  the  outlet ;  it  is  being  built  in  open  cut  through 
wet  clay  and  loam,  which  is  excavated  by  hand,  and  hoisted 
and  back-filled  by  a  Carson-Lidgerwood  cableway  of  about 
300  feet  span. 

COSTS. 

Cost  is  such  a  variable  quantity  that  only  very  rough  figures 
can  be  given.  For  small  tunnels  of  from  30  to  100  square  feet 
section  in  good  solid  rock  free  from  bad  seams,  the  cost  per  cubic 
yard  should  not  exceed  $4.00  to  $10.00  For  tunnels  of  from 
100  to  300  square  feet  section,  $3.75  to  $8.00  per  cubic  yard, 
and  for  tunnels  -from  300  to  600  square  feet,  $3.50  to  $6.50  per 
cubic  yard. 

The  cost  of  excavation  for  tunnels  through  earth  is  even  a 
greater  variable  than  that  for  rock,  but  taking  the  experience 
gained  in  several  tunnels  through  wet  earth,  it  might  be  placed 
as  follows:  Tunnels  having  an  excavated  area  of  30  to  100 


HYDRAULIC  CONSTRUCTION. 


199 


square  feet  section  cost  $7.00.  per  cubic  yard,  Tunnels  of  100 
to  300  square  feet  area  $6.00  per  cubic  yard,  and  for  tunnels 
of  500  square  feet  area  and  larger,  $5.00  per  cubic  yard.  These 
are  perhaps  a  little  bit  high,  but  should  be  safe.  One  tunnel 
30  by  40  feet  cost  $2.00  per  cubic  yard.  The  cost  of  the  mate- 
rials for  lining  is  not  included  in  either  the  prices  for  rock  or 
earth  excavation. 

A  tunnel  of  45  sq.  ft.  area  in  hard  red  clay  and  slate  cost 
all  complete  $8.28  per  cu.  yd.,  as  follows: 

Excavation,  labor,  at  $2  .............................   $6.  65 


Blacksmith  and  repairs 

Bailing  water 

Dynamite  at  13c.,  caps  at  3Jc 

Coal  and  oil 

Lumber  in  shaling  at  $32 

Labor  in  shaling  at  $2 


25 
17 
22 
21 

32 
46 


$8.28 

Trenches  in  Rock  (Kidder). 
Trench  three  feet  wide  (   Drillin^  -$L5°  to  $2'50  Per  cubic  ^ard 


out..         .30  to      .40    " 


$2.20  to  $3.40    " 


Trench  six  feet  to  ten 
feet  wide  in 
Hard  trap  rock 


Drilling $.50  to  $.70  per  cubic  yard 

Explosive..    .30  to    .40    " 
Throwing 

out 25  to    .35    " 

$1.05  to  $1.45    "       " 


PENSTOCKS. 

Penstock  is  the  name  given  to  that  part  of  the  headworks 
which  carries  the  water  and  performs  no  other  office. 
The  penstock  usually  ends  in,  and  becomes  a  part  of  the  flume 
but  in  the  flume  the  water  brought  by  the  penstock  is  trans- 
formed into  power.  The  nearest  thing  to  a  penstock  is  a  race 
or  canal,  and,  in  fact,  they  perform  the  same  duty,  only  the 
penstock  is  built  of  some  material  other  than  earth. 


200 


H  YDROELECTRIC  PLA  N TS . 


The  cheapest  penstocks  are  built  of  timber.  Fig.  177  shows 
a  square  timber  penstock  open  at  the  top  and  not  intended  to 
run  entirely  full.  In  this  case  the  cap  A  is  wholly  a  tension 
member.  The  post  B  must  be  of  sufficient  size  to  resist  the 
pressure  due  to  the  head  H.  This  pressure  will  act  as  a  point  P, 
one-third  the  distance  H  up  from  the  bottom  end 

IT 

W   =  —  X  62,  5X//X  1   ;=  total  press  against  post. 

The  size  of  post  is  then  found  from  case  (5,)  (page  123) 
The  proper  thickness  of  the  plank  will  depend  on  the  distance 
7,  which  is  selected  in  such  a  way  that  the  materials  saved  by 
thinning  the  plank  will  not  add  more  to  the  frame  than  that 
saved.  There  is  a  proportion  of  frame  and  plank  which  is  the 
cheapest,  and  this  must  be  found  by  trial.  Table  XXXVI 
gives  the  thickness  of  plank  for  any  span  /  and  head  H. 


PLANK.  UNDER  WATER  PRESSURE 


TABLE  XXXVI. 

THICKNESS  OF  PLANK  TO  SAFELY  SUSTAIN  THE  HEAD 


SPAN. 

40  ft.  head 

30  ft.  head. 

20  ft.  head. 

10  ft.  head. 

5  ft.  head 

3  feet 

3^  ins 

3       ins. 

2H 

2  #  thick 

1M  ins 

4     " 

4H     " 

4 

zy* 

2H      " 

2X     " 

6     " 

6M     " 

6 

5X 

4^      " 

3H     " 

8     " 

9 

8 

7 

5H      " 

4H     " 

10     " 

11M     " 

10 

8% 

7 

5H     " 

12     " 

13Ji     " 

12  \i     " 

10** 

8H      " 

6H     " 

FIG.  177. 

The  penstock  shown  in  Fig.  177  may  be  planked  across  the 
top  and  used  full  of  water,  and  under  a  load  higher  than  the 
cap  A. 

Fig.  178  shows  a  form  of  rectangular  penstock  which  possesses 
some  of  the  advantages  of  the  stave-pipe  penstock.  As  will  be 
seen,  it  can  be  tightened  up  by  means  of  the  rods  b.  Such  a 


HYDRAULIC  CONSTRUCTION. 


201 


penstock  costs  more  to  build  than  the  one  just  described,  unless 
timber  is  very  expensive  and  iron  is  cheap,  but  cheaper  sheeting 
can  be  used,  because  of  the  ease  with  which  it  may  be  clamped 
up  tightly.  It  requires  more  iron  than  a  stave  pipe  of  the 
same  capacity  and  costs  more  to  build. 


FIG.  178. 

Frequently  the  penstock  is  made  as  in  Fig.  179.  In  this  plan 
the  posts  do  not  have  to  be  as  heavy  as  in  the  preceding,  and 
there  is  no  cap,  but  the  braces  are  added  and  the  sill  lengthened. 

In  place  of  a  cap  or  bracket  t,  an  iron  rod  may  be  used  to  hold 


FIG.  179. 


W 

the  tops  of  posts.     The  stress  at  tops  of  posts  =  —  where  W  is 

3 

the  water  pressure  as  found  above,  and  the  horizontal  stress  at 

2 
the  foot  of  post  =  —  W,  when  the  penstock  is  planked  to  the 


202 


HYDROELECTRIC  PLANTS/ 


top  of  posts  and  is  full  of  water.  Of  course  the  less  the  depth 
of  water  the  more  the  proportionate  stress  on  the  foot  and  the 
less  at  the  top. 

With  the  growing  scarcity  of  timber  it  frequently  happens 


FIG.  180. 

that  small  lumber  must  be  used,  in  which  case  a  penstock  may 
be  constructed  as  shown  in  Fig.  180.  As  here  shown  the  frame 
is  made  entirely  of  planks  two  inches  thick  by  eight  inches  wide. 
This  particular  penstock  was  made  as  part  of  the  trestle  and 
proved  to  be  a  very  satisfactory  one. 


FIG.  181. 


A  penstock  possessing  certain  advantages  is  shown  in  Fig. 
181.  The  timbers  C  and  D  may  cut  off  any  segment  desired. 
The  iron  bands  A  serve  to  tighten  up  the  staves;  E  is  a  2x8 
plank,  spiked  on  the  lower  end  of  the  cap  for  the  top  stave  to 


/-/ YDRA  ULIC  CONSTR UCTION. 


203 


butt  against.  Flash  boards  were  set  up  along  the  top  edges,  as 
B,  to  hold  the  water  up  over  the  cap  C,  and  thus  prevent  its 
rotting.  This  penstock  is  in  use  at  Raymondville,  N.  Y.,  by 
the  Raymondville  Paper  Company.  The  one  serious  defect  is 
the  certainty  that  the  sill  D  will  soon  decay.  If  this  were  a 
reinforced  concrete  beam  the  design  would  be  very  good  for  an 
open  penstock. 

Penstocks  built  of  wood  staves  and  of  circular  sections  (Fig. 
182)  are  without  doubt  the  most  efficient  and  cheapest  of  all  the 
many  forms,  since  they  possess  the  great  advantages  of  perma- 
nence and  tightness.  Common  laborers  under  a  good  foreman 
can  construct  this  penstock,  and  at  any  time  any  part  may  be 
tightened  up.  The  pipe  does  not,  of  course,  have  to  run  full  of 


FIGS.  182,   183. 

water,  though  when  it  carries  water  under  pressure  it  works 
at  its  greatest  efficiency. 

The  staves  are  made  of  any  good  wood,  but  cedar,  hard  yellow 
pine,  and  fir  are  the  best.  Sound  knots,  if  not  more  than  one 
inch  in  diameter,  are  allowable,  but  there  must  be  no  sap-rot, 
shakes  or  waney  edges.  It  is  of  the  greatest  importance  to 
have  the  inside  surface  of  the  'taves  surfaced  smooth  in  order 
to  reduce  the  friction  and  increase  the  capacity  of  the  pipe. 
The  staves  may  be  four,  six  or  eight  inches  wide,  and  the  thickness 
will  depend  on  the  spacing  of  the  hoops  and  the  pressure  in  the 
pipe.  As  in  the  case  of  the  timber  penstock,  there  is  a  certain 
thickness  of  stave  and  spacing  of  hoop  which  is  the  most  econ- 
omical. As  this  proportioning  of  the  parts  depends  on  the  cost 
of  the  materials  we  will  not  attempt  to  give  any  data  on  the 
subject. 

The  usual  joint  at  the  end  of  staves  is  shown  in  Fig.  183.    The 


204 


HYDROELECTRIC  PLANTS. 


ends  are  sawed  square  and  a  kirf  is  sawed  in  with  a  cross-cut  saw. 
A  template  should  be  used  in  sawing  the  kirfs  in  the  ends  of 
staves,  as  shown  in  Fig.  184.  The  fillet  is  just  thick  enough  to 
allow  the  saw  to  enter  between  the  hard  wood  guides.  With 
such  an  appliance  two  men  can  easily  keep  a  pipe  gang  of  four 
men  supplied.  An  iron  tongue  1J  inches  by  width  of  stave 
+  J  inch,  and  J  inch  thick  is  slipped  into  the  slot  after  the  stave 


'   • 

T]                   /** 

H 

*~ 

0 
0 

3 

^"U 

x-«/  >«><?</ 

i^f^r 

3}       *»« 

1           A 

A                     ^*^ 

FIG.  184. 

has  been  put  into  the  pipe,  as  shown  in  Fig.  183.  Being  \  inch 
longer  than  the  space  the  ends  crush  into  the  staves  and  form 
a  water-tight  joint.  These  tongues  should  be  galvanized,  other- 
wise they  will  rust  out  in  the  course  of  four  or  five  years. 

The  opinion  of  the  author  is  that  the  best  stave  joint  is  the 


FIGS.  185,   186. 

one  shown  in  Fig.  185.  In  this  joint  there  is  no  iron  to  rust,  and 
the  tongue  being  of  wood  arid  exactly  the  width  of  the  stave, 
will  swell  tight.  To  saw  these  ends  requires  a  special  saw,  some- 
thing like  that  shown  in  Fig.  ISO.  Of  course  such  a  sawing  outfit 
is  expensive,  the  one  shown  costing  $150,  but  on  long  pipe  lines 
the  steel  tongues  saved  will  more  than  pay  for  the  cost.  With 
such  a  sawing  outfit  a  stave  can  be  sawed  in  much  less  time 
than  the  ends  shown  in  Fig.  183  could  be  sawed  by  hand.  The 


HYDRAULIC  CONSTRUCTION. 


pipe  line  for  which  the  above  saw  was  made  was  composed  of 
45,000  staves  or  90,000  ends.  A  saving  of  18,000  pounds  of 
tongue  iron  was  affected,  which,  with  iron  at  three  cents  a 


FIG.  187. — Stave  penstock. 

pound,  saved    $540,  and  fully  as  much  again  was  saved  on  the 
sawing. 

In  building  the  pipe  a  tool  called  an  expander  is  used  to 


.     FIG.  188. 

keep  the  pipe  a  true  circle.  This  is  shown  in  Figs.  187  and  188. 
The  expander  is  kept  out  to  the  full  diameter  while  the  hoops 
are  being  placed,  as  the  rods  are  tightened  the  expander  is  con- 
tracted by  turning  the  handle. 

Fig.    188  shows  the  end  of  expander.     In  the  end  of  each 


206 


HYDROELECTRIC  PLANTS. 


segment  B  is  an  iron  D  which  works  in  a  slot  in  the  head  C. 
The  expander  shown  will  do  for  pipes  up  to  four  feet  in  diameter, 
but  beyond  that  men  can  work  inside  the  pipe  and  a  simple 
device  like  Fig.  189  is  used.  It  consists  of  a  disc  of  wood  whose 
diameter  is  exactly  the  size  of  the  pipe,  and  having  the  two 
segments  mounted  on  hinges  as  shown.  When  the  hoops  have 
been  tightened  some,  the  hinged  parts  are  knocked  back  and  the 
disc  moved  along.  A  manhole  is  provided  so  that  workmen 
can  pass  through. 

Round  iron  is  usually  used  for  hoops  though  flat  iron  is 
sometimes  best  for  very  heavy  work.  Round  iron  crushes  into 
the  wood  some  and  thus  relieves  the  pressure  caused  by  the 
swelling  of  the  wood.  It  is  also  ready  to  thread  and  may  be 
cut  to  any  length.  A  hoop  smaller  than  ^-inch-round  iron  should 
never  be  used  on  account  of  the  effects  of  rapid  rusting.  To 


FIG.  189. 

allow  for  the  rusting  away  and  the  swelling  of  the  wood,  a 
factor  of  safety  of  eight  should  be  used.  Fig.  190  will  be  found 
useful  in  getting  the  proper  size  of  hoop.  The  left  hand  ordinate 
gives  the  pressure  in  pounds  per  linear  inch  of  pipe. 

EXAMPLE. — A  pipe  10  feet  in  diameter  under  500  feet  head 
has  a  pressure  of  13,000  pounds  per  inch  length,  tending  to 
part  the  two  halves  of  the  pipe  and,  if  a  rod  is  used  every  inch 
of  the  pipe's  length  to  hold  the  pressure  of  500  feet  head,  it 
will  have  to  have  a  safe  strength  of  13,000  pounds.  If  the 
rods  are  spaced  six  inches  apart,  each  rod  will  have  to  have  a 
safe  strength  of  13,000X6,  or  78,000  pounds.  If  the  pipe  is 
made  of  metal,  the  material  must  be  such  as  to  safely  resist 
the  pressure  of  13,000  pounds  per  inch  length.  Assume  the 
metal  is  J-inch  thick,  it  must  then  have  a  safe  tensile  strength 
of  26,000  pounds  per  square  inch.  In  this  way,  the  table  may 


HYDRAULIC  CONSTRUCTION. 


207 


be  used  for  spacing  of  hoops  and  for  any  kind  of  metal  pipe. 
The  diameter  of  the  rod  should  be  taken  at  bottom  of  the 
threads. 

The  shoes  or  dogs,  are  usually  of  cast  iron  and  made  separate 
from  the  hoop.      The    author    has    found   the   shoe   shown  in 


7    8    9    /O  //    /2»  .  /3  /4-   /&  /6  /7 

D/&f77.  offrpe  //?/&<?/• 


FIG.  190. 

Fig.  191  to  be  the  cheapest  and  best  to  use.  This  one  is  designed 
for  a  f-inch  rod.  Its  advantages  are  that  the  hoop  does  not 
have  to  be  strung  through  a  round  hole  but  simply  bent  over 
into  it.  On  jobs  of  any  size  it  is  a  good  plan  to  make  socket 
wrenches  with  auger  handles  for  tightening  up  the  hoops. 


208 


HYDROELECTRIC  PLANTS. 


COSTS. 

Fig.  192  gives  the  cost  per  foot  of  reinforced  concrete  pen- 
stock. The  data  from  which  this  curve  is  plotted  was  derived 
largely  from  Gillette's  book,  "  Cost  Data,"  but  also  from 
numerous  other  sources. 


FIG.  191. 

Reinforcing  costs  about  three  cents  per  pound  for  steel, 
and  C.5  cent  to  instal.  The  concrete  costs  bout  $10.00 
per  cubic  yard,  including  every  item.  Round  rods  cost  about 


FIG.  192. 


$34.00  per  ton.  Brick  penstocks  require  570  bricks  per  cubic 
yard  and  1.25  barrels  of  cement.  A  mason  should  lay  1200 
bricks  in  eight  hours  at  a  cost  of  $6.00 

Figs.  193  to  195  show  the  three  common  forms  of  steel  riveted 


H YDRA  ULIC  CONSTR UCTION. 


209 


FLANGED    ENTRANCE     TAPER 
BOLTED  TO  PRESSURE     BOX 


FIGS.  193-195. 


210  HYDROELECTRIC  PLANTS. 

pipe.  Fig.  193  shows  the  common  slip  joint,  one  end  being 
tapered  so  as  to  drive  tightly  into  the  preceding  section.  The 
fit  of  the  ends  is  alone  depended  on  to  secure  a  water-tight 
connection,  no  riveting  being  done.  Such  joints  should  not  be 
used  for  heads  exceeding  250  feet. 

Fig.  194  shows  a  butt  joint,  leaded.  In  this  type  of  joint 
the  ends  butt  squarely  against  each  other.  A  sheot  non  sleeve 
is  riveted  on  the  inside  of  a  section  as  shown  and  the  next  length 
placed  over  the  projecting  one.  A  steel  collar  about  f-inch 
larger  inside  diameter,  than  the  outside  diameter  oi  pipe,  is 
then  placed  around  the  joint  and  run  full  of  lead,  and  securely 
caulked.  This  joint  can  stand  a  head  of  600  feet 

The  flanged  joint,  Fig.  195,  is  perhaps,  the  best  joint  for 
heads  above  600  feet,  and  can  be  made  for  any  pressure.  The 
figure  is  self-explanatory. 

The  most  common  point  of  failure  is  the  breaking  of  the 
flange  and  not  the  stripping  of  the  thread.  The  end  of  the 
pipe  should  be  screwed  an  eighth  of  an  inch  beyond  the  face 
of  the  flange  so  that  it  will  press  against  the  packing.  The 
faces  of  the  flanges  should  be  planed  smooth  and  corrugated 
male  and  female.  Rainbow  or  copper  gaskets  are  ased  between 
the  flanges. 

There  has  long  been  a  strong  prejudice  against  the  use  of 
thin  steel  for  water-pipes  on  account  of  the  rapidity  with  which 
they  rust  out.  The  Pelton  Water  Wheel  Company  of  San 
Francisco  claim  that  they  greatly  retard  the  rusting  process 
by  boiling  the  sheet  steel  in  hot  asphaltum.  A  great  advantage 
possessed  by  this  pipe  is  its  lightness,  making  transportation 
easy.  Long  straight  steel  pipes  must  have  expansion  joints. 

THE    DESIGNS    OF    DAMS. 
MATS  ON  SOFT  BOTTOMS. 

Under  this  heading  all  bottoms  other  than  solid  stone  are 
included.  A  great  deal  of  care  must  be  taken  in  selecting  a 
good  bottom. 

The  most  common  river  bed  is  one  having  large  round  stones 
on  top  of  gravel,  and  the  gravel  covering  a  stratum  of  clay  or 
sand,  usually  the  latter. 

Frequently  this  layer  of  stone  and  gravel  is  quite  thin,  being 
merely  a  film  covering  the  most  dangerous  sand.  An  iron  rod 


HYDRAULIC  CONSTRUCTION. 


211 


can  hardly  be  driven  into  such  coverings,  and  hence  often 
leads  the  engineer  to  think  that  the  bottom  is  a  good  one. 

Dams  on  such  bottoms  must  be  placed  on  some  form  of  mat, 
and  at  least  one  row  of  sheet  piling  must  be  driven.  Fig.  196 
shows  a  mat  under  construction.  Here  the  gravel  and  boulder 
covering  was  part  way  directly  upon  the  clay,  and  part  way 
over  very  elusive  sand.  Sheet  piling  could  not  be  driven  through 
this  layer,  so  trenches  were  dug  as  shown. 

Hard  pan  is  a  name   given  to  a  hard  clay  mixed  with  small 


FIG.  196. 


stone.  It  is  very  hard  and  has  to  be  picked  or  blasted. 
Bottoms  of  hard  pan,  provided  the  hard  pan  is  thick 
enough,  may  be  built  upon  direct,  without  the  use  of  a  mat, 
piling  cannot  be  driven,  so  a  seepage  trench  similar  to 
the  one  shown  in  Fig.  237  is  used  to  prevent  seepage 
underneath.  The  hard  pan  may  be  overlaid  with  some 
softer  material,  as  sand  or  gravel,  in  which  case  great  caution 
must  be  observed.  Where  possible  the  soft  bottom  should  be 
excavated  and  the  dam  placed  on  the  hard  pan.  Where  the 


21-'  HYDROELECTRIC  PLANTS. 

depth  is  too  great  to  make  this  possible,  sheet  piling  must  be 
driven.  Where  the  hard  pan  is  only  three  or  four  feet  from  the 
surface,  there  is  danger  that  the  seepage  confined  within  narrow 
limits  will  cause  undermining.  Under  such  conditions  the 
sheet  piling  must  be  even  more  nearly  water-tight  than  would 
be  necessary  were  the  hard  pan  ten  or  more  feet  down. 

When  the  bottom  is  of  sand  every  precaution  known  to  the 
profession  should  be  used.  When  contained,  sand  makes  a 
perfect  foundation,  but  if  allowed  ever  so  small  an  outlet  it 
will  run  like  so  much  oil.  There  is  a  great  difference  in  river 
sand  with  regard  to  difficulty  in  building.  A  sharp  coarse 
sand  is  safety  itself  compared  with  some  of  the  fine  dull  sand 
found  in  the  Western  rivers. 

On  sand  bottoms  the  width  of  the  mat  should  be  about  four 
times  the  height  of  the  dam,  and  a  very  heavy  extension  mat 


FIG.  197. 

must  be  provided.  A  row  of  water-tight  sheet  piling  must 
be  driven  along  each  edge  of  the  mat.  These  should  be  jetted 
down,  unless  they  are  of  steel.  On  the  worst  bottoms  the  piling 
should  be  from  18  feet  to  100  feet  long,  depending  on  the  height 
of  dam.  Nothing  must  be  placed  under  the  mat  to  hold  it  up, 
other  than  the  sand,  as  the  entire  weight  of  the  dam  and  water  is 
required  to  press  the  mud  sills  into  the  sand.  Many  dams 
have  been  undermined  because  they  were  placed  upon  piling. 
The  sand  settled  as  in  Fig.  197,  and  though  sheet  piling  was 
driven,  enough  wat  seeped  through  to  cause  a  washout. 

There  is  always  more  or  less  seepage  through  sand.  The 
voids  are  full  of  water  and  water  pressure  at  one  point  is  in- 
stantly transmitted  to  more  distant  points.  Thus  if  the  mat 
is  laid  upon  the  sand  and  more  water  seeps  through  the  up- 
stream sheet  piling  than  through  the  down-stream  row,  there 


HYDRAULIC  CONSTRUCTION.  213 

will  be  an  uplift  on  the  under  side  of  the  entire  mat.  Therefore, 
outlets  must  be  provided  through  the  top  of  the  mat.  Usually 
where  the  worst  sand  is  found  there  will  be  no  stone  for  riprapping 
and  concrete,  but  gumbo  and  sand  are  apt  to  abound,  and 
with  these  rock  may  be  created. 

MATS  ON    PART   ROCK  AND   PART     SOFT   BOTTOM. 

A  condition  sometime^  met  with  is  as  in  Fig.  198.  Here 
the  bottom  is  rock  part  way  and  sand  the  rest  of  the  way. 
Where  the  rock  drops  down,  as  at  a,  a  wall  is  built  for  the  mat 
to  abut  against.  The  mat  has  no  connection  with  this  wall, 
as  it  would  be  held  up  from  pressing  the  sand  underneath  and 
a  leak  would  collow  the  wall.  This  wall  is  built  up  above  the 


FIG.  193. 

crest  of  the  dam.  At  B  the  wall  is  carried  out  toward  soft 
bottom  and  down  to  rock,  to  a  depth  of  six  or  eight  feet  or 
more,  and  the  first  sheet  pile  imbedded  in  it  as  at  B.  This 
shuts  off  all  leakage  and  yet  does  not  suspend  the  end  of  the 
dam  over  the  soft  bottom.  The  large  dam  at  Lowell,  Mass, 
is  an  interesting  example  of  a  dam  built  partly  on  rock  and 
partly  on  soft  bottom.  It  has  been  a  constant  source  of  ex- 
pense on  account  of  the  method  of  building. 

MATS  ON  ROCK   BOTTOMS. 

Dams  built  upon  rock  are  not  necessarily  built  on  a  safe  founda- 
tion.    To   be   safe  the   rock   must   be   free   from   seams  which 
•would  conduct   water  under  the  dam.     The  Austin  dam  was 
supposed  to  be  built  on  a  solid  ledge,  but  water  went  under  the 
dam   and   came   out   far  below.     Deep   sounding   with   a  core 


214 


HYDROELECTRIC  PLANTS. 


drill  (page  57) ,  is  the  only  way  to  make  sure ;  but  for  small  dams 
a  seepage  trench,  see  Fig.  237  will  be  sufficient,  and  in 
the  excavation,  show  up  the  nature  of  the  rock.  The  pro- 
portions of  the  seepage  trench  will  depend  on  the  nature  of  the 
bottom  and  whether  the  safety  of  the  dam  depends  solely  on 
the  gravity  of  the  masonry  or  upon  the  gravity  of  the  im- 
pounded water. 

If  the  former  it  should  be  wide  enough,  up  and  down  stream, 
to  afford  the  proper  shearing  strength  (unless  the  entire  dam 
is  set  down  into  the  rock  as  in  Fig.  237,  to  resist  the  total 
down-stream  thrust  of  the  water.  If  the  dam  is  of  the 
gravity  type  the  trench  need  only  be  wide  enough  to  prevent 
water  seeping  through. 

On  bottoms  that  are  not  too  yielding — such  as  sand  and 
silt — the  mat  may  be  made  of  concrete  and  steel,  and  at  a  cost 


FIG.  199. 


of  about  the  same  as  timber  when  concrete  can  be  made  for 
$5.00  per  cubic  yard  and  timber  costs  $30.00  per  thousand. 

Such  a  mat  is  shown  in  Fig.  199.  The  reinforcing  consists 
of  |  steel  rods.  At  the  points  between  sections,  as  at  A, 
thin  tar-paper  is  placed  during  the  lay'ng  of  the  concrete,  so 
that  in  settling  the  mat  will  not  break  into  irregular  cracks. 

The  cost  of  this  mat  laid  on  bottom  fairly  level  would  be 
about  20  cents  per  square  foot.  The  rods  will  cost  1J  cents 
per  square  foot,  and  the  concrete  should  easily  be  laid  for  $5.00 
per  cubic  yard.  In  all  foundation  work  it  is  very  important  to 
work  in  the  dry,  and  the  time  saved  and  superior  excellence 
of  the  work  will  pay  for  a  liberal  expenditure  for  coffer  dams 
.and  pumping. 


HYDRAULIC  CONSTRUCTION. 


215 


EXTENSION     MAT. 

There  are  very  few  bottoms  where  a  mat  is  required,  which 
do  not  also  demand  the  use  of  an  extension  to  conduct  the 
water  away  from  the  dam  in  safety. 

One  of  the  most  common  methods  is  to  build  a  heavy  crib 
below  the  mat  and  fill  it  with  stone  (see  Fig.  200).  The  crib 
is  not  attached  to  .the  mat,  but  is  held  in  position  by  heavy 


FIG.  200. 

round  piles  a,  driven  at  six-foot  to  ten-foot  intervals.  This 
allows  the  crib  to  settle  without  pulling  away  from  the  mat. 
This  crib  should  take  all  the  pounding  there  may  be,  and  thus 
save  the  dam  from  the  vibration.  The  deck  should  be  of  oak 
from  four  to  six  inches  thick.  The  proportions  of  the  crib  will 
depend  entirely  on  the  nature  of  the  bottom,  but  it  is  usually 


FIG.  201. 


best  to  get  the  desired  degree  of  safety  from  the  undermining 
by  making  the  crib  long  rather  than  deep. 

Another  form  of  mat  which  possesses  many  good  points  is 
shown  in  Fig.  201.  This  consists  of  a  series  of  wooden  boxes, 
having  plugs  in  the  ends,  and  filled  with  sand.  Each  box  is 
strung  on  two  chains,  as  at  A,  running  across  the  river.  If  a 
longer  extension  than  16  or  18  feet  is  required,  another  section 
may  be  attached,  as  shown.  The  extension  is  fastened  to  the 


216 


HYDROELECTRIC  PLANTS. 


mat  with  links  passing  through  the  piling,  and  the  intermediate 
sill.  Such  a  mat  is  perfectly  flexible,  and  will  continue  to  settle 
as  long  as  there  is  any  wash. 

About  the  cheapest  kind  of  an  extension  mat  is  that  shown  in 
Fig.  202.  It  is  hardly  a  safe  construction  where  the  bottom 
is  sand,  as  the  back  wash  works  back  under  the  flooring  an  in- 
credible distance.  The  pilings  must  be  driven  deep,  as  they 
often  have  to  resist  severe  uplifts  from  ice,  and  this  at  a  time 


FIG.  202. 

when  the  earth  may  be  washed  away  for  half  their  length  or 
more.  The  piles  should  be  driven  at  intervals  of  from  six  to 
eight  feet  across  the  river. 

GRAVITY    DAMS. 

The  gravity  dam  is  one  of  the  oldest  types,  but  it  is  only 
within  the  last  few  years  that  it  has  become  a  prominent  type 
of  construction.  To  more  clearly  understand  the  theory  of 
the  gravity  dam  we  will  investigate  the  action  of  the  water 


FIGS.  204,  205,  206. 

in  the  three  cases  (Figs.  204-206),  Fig.  204:  here  the  water  acts 
at  P  and  is  wholly  a  horizontal  force  tending  to  shove  the  dam 
down  stream.  This  pressure  can  be  figured  with  great  exact- 
ness, and  =  \  H  X  H  X  the  weight  of  a  cubic  foot  of  water,  the 
only  factor  of  uncertainty  being  the  weight  of  water  and  the 
extreme  of  variation  for  all  altitudes  and  temperatures  is  only 
0.5  per  cent.,  62.41  pounds  per  cubic  foot  being  the  maximum 
weight ;  Fig.  205 :  in  the  case  of  a  dam  having  a  slope  up  stream  of 
45°,  we  have  the  same  down-stream  pressure  as  in  Fig.  204 


HYDRAULIC  CONSTRUCTION.  217 

(H  being  the  same),  but  we  also  have  a  vertical  pressure.     Sup- 
on 
pose  H  =  20  then  the  horizontal  P  =  ~  X 20X62. 5  =  12500 

pounds  per  foot  length  of  dam.  We  have  a  vertical  pressure 
equal  to  the  weight  of  the  triangle  of  water,  ,-1  B  C,  immediately 

TT 

over  the  dam  =  —  X-RX62.5.     As    R  =  H    in    this    case,    the 

horizontal  and  vertical  pressures  are  equal.  If  there  were  no 
friction  between  the  dam  and  the  bed  of  the  stream  the 
dam  would  be  just  ready  to  slide.  Fig.  206:  here  we  have 
an  exaggerated  gravity  dam  where  practically  all  the 
pressure  is  vertical,  and  at  any  point  N  the  pressure  is 
perpendicular  to  the  deck  and  almost  perpendicular  to  the 
base  of  the  dam.  The  horizontal  pressure  on  the  dam  de- 
pends solely  on  the  depth  of  water,  and  is  the  same  for  all 
forms,  but  the  vertical  pressure  for  equal  depths  of  water  may 
be  made  to  assume  any  desired  value  by  changing  the  form  of 
the  dam.  This  pressure  is  found  by  multiplying  the  depth  of 
water  above  N  by  62.5,  which  gives  the  pressure  per  square 
foot  on  the  deck.  Suppose  a  post  S  is  used  to  resist  this  pres- 
sure and  the  distance  between  posts  across  the  stream  (distance 
between  bents)  is  four  feet,  and  the  distance  up  and  down  stream 
between  lines  of  posts  is  four  feet,  then  the  posts  will  sustain 
an  area  of  deck  equal  to  four  times  four,  or  16  square  feet.  This 
multiplied  by  the  pressure  per  square  foot  gives  the  pressure 
on  the  post,  and  the  post  may  then  be  designed  as  exactly  as 
can  a  compression  member  in  a  bridge,  and  even  more  so,  because 
the  load  is  a  constant  one.  If  the  water  stands  10  feet  above 
the  crest  of  the  dam  625  pounds  of  pressure  are  added  to  each 
square  foot  of  the  deck's  surface.  The  deck  is  usually  attached 
to  plates,  as  at  L,  in  which  case  the  span  between  posts  (in  this 
case  four  feet),  and  the  plates  being  four  feet  apart,  each  plate 
sustains  16  square  feet  of  the  deck,  or  16  t'mes  the  pressure  per 
square  foot  on  the  deck.  Therefore  we  have  a  beam  four  feet 
long  carrying  a  uniform  load,  and  from  tables  we  find  the  proper 
size  of  beam,  using  any  factor  of  safety  we  may  choose.  Here 
all  uncertain  factors  are  eliminated  and  the  design  of  the  dam 
becomes  simply  a  question  of  strength  of  materials.  The  posts 
are  placed  at  right  angles  to  the  deck  and  in  direct  line  with  the 
thrust  of  the  water. 


218 


HYDROELECTRIC  PLANTS. 


The  flatter  the  dam  the  greater  the  pressure  down  upon  the 
river  bed;  therefore  for  dams  on  sand  bottoms  the  slope  should 
not  be  greater  than  30°;  23°  is  about  as  flat  as  necessary  for  the 
softest  bottom,  and  for  dams  on  rock  bottoms  45°  may  be  used. 

One  of  the  oldest  types  of  the  gravity  dam  is  the  crib  dam. 
Usually  it  was  filled  with  stones  and  earth.  Fig.  207  shows 


FIG.  207. — Common  form  of  crib  dam. 
i 

such  a  dam,  built  entirely  of  4x8-inch  timbers,  all  spiked  together 
to  form  numerous  cells,  each  about  six  feet  square.  In  this 
particular  dam  the  cells  were  filled  with  gravelly  dirt,  thoroughly 
wet  down.  This  is  a  fair  type  of  the  crib  dam.  Frequently 
logs  are  used  instead  of  the  4x8-inch  timbers,  and  the  dam 
filled  with  ~stone.  In  nearly  every  case  where  the  bottom  is 
soft,  the  dam  is  supported  on  piling.  A  dam  is  built  to  utilize 


FIG.  208. — Pile  dam. 

the  holding-down  force  of  the  water,  and  then  expensive  piling 
is  driven  to  hold  the  dam  up  off  the  bottom. 

In  this  dam  there  is  no  means  of  entering  the  interior,  so  that 
the  timbers  may  be  inspected  and  renewed  at  will.  Filling  with 
earth  or  even  stone  hastens  decay  and  adds  nothing  to  the  secur- 
ity of  the  structure.  Such  dams  are  usually  filled  above  with  earth 
(Fig.  208) ,  gravel  and  boulders.  Boulders  make  the  very  worst 


HYDRAULIC  CONSTRUCTION. 


219 


filling  possible  when  it  is  desired  to  stop  seepage.  In  fact  they 
make  a  drain  rather  than  a  stop-water.  A  common  form  of 
crib  gravity  dam  for  soft  bottoms  is  shown  in  Fig.  209,  and  for 
rock  in  Fig.  210.  All  the  cribs  are  filled  with  stone.  The  tim- 
bers are  mostly  10x10  inches,  and  the  apron  is  of  12xl2-inch 
timbers.  The  apron  is  shown  without  the  planking.  This  dam 


FIG.  209.— Crib  dam. 

stood  for  about  50  years.  The  bottom  was  boulders,  gravel 
and  sand.  This  is  a  very  good  construction,  the  chief  criticism 
being  that  too  much  material  is  used,  that  it  cannot  be  entered 
for  inspection,  and  that  decay  is  increased  by  such  masses  of 
heavy  timber. 

Every  timber  entering  into  the  construction  of  a  dam  should 


FIG.  210.— Crib  dam. 

be  proportioned  to  the  load  it  is  to  sustain.  This  is  for  two 
reasons,  cost  and  longevity.  It  is  a  well-known  fact  that  a  large 
timber  will  rot  more  quickly  than  will  a  small  one.  In  a  large 
stick  the  heart  decays  first,  and  while  the  outside  may  seem  to 
be  sound,  the  interior  becomes  soft  and  devoid  of  strength. 
Every  timber  should  be  accessible  for  inspection  and  repair. 
The  interior  of  the  dam  should  be  ventilated  to  keep  down  the 


220 


HYDROELECTRIC  PLANTS. 


temperature,  which  is  at  all  times  higher  than  the  outside  air 
A  large  portion  of  the  timber  should  at  all  times  be  in  direct 
contact  with  the  water. 

The  dams  shown  in  Figs.  207  and  209  are  resting  on 
mats  of  solid  timber  and  bolted  thereto.  In  Fig.  207  the 
mat  is  supported  on  piling,  but  in  Fig.  209  it  rests  on  the  river 
bottom.  The  mat  is  an  essential  feature  of  all  dams  on  soft 
bottoms,  and  should  possess  the  following  features:  It  should 
extend  under  the  entire  dam  and  the  abutments.  It  should 
have  a  specific  gravity  heavier  than  water.  It  should  be  flexible. 
All  of  the  sills  in  contact  with  the  bottom  must  run  across  the 
stream  and  not  up  and  down  stream.  The  mat  must  not  be 
supported  on  piling.  It  must  have  at  least  one  row  of  sheet 
piling  along  the  edges. 


:^^f§!! 

{$$?'  <&?& £feV£7//0/?  "^S 

"•#'•':''  '-x\>.V:" 


FIG.  211. — Beardsley  mat. 

In  Fig.  211  the  essential  features  of  a  patent  mat  possessing 
all  the  above  features  are  given.  The  mat  is  built  so  that  it  is 
at  all  times  submerged.  It  can  therefore  be  built  of  any  sound 
lumber.  The  mud  sills  A  are  first  laid  in  the  river  bed.  Where 
possible  the  river  bed  should  be  excavated  rather  than  filled  up 
to  a  level.  That  is,  the  top  surfaces  of  the  mud  sills  should  be 
placed  level  with  the  natural  river  bed,  the  trenches  being  dug  for 
them.  When  this  cannot  be  done  the  fill  may  be  made  with  any 
material  that  will  not  be  dissolved  by  the  action  of  the  water. 
An  architect's  level  is  indispensable  in  laying  these  sills.  One 
man  holds  the  staff  on  the  ends  of  the  sills  and  the  other  men 
tamp  under  the  sills  until  they  are  level,  then  the  timbers  are 


HYDRAULIC  CONSTRUCTION.  221 

weighed  down  to  prevent  floating  out  should  the  pumps  stop. 
When  the  sills  are  levelled  they  are  filled  flush  to  their  tops,  a 
straight  edge  being  used  to  level  with. 

If  too  much  fill  is  used  the  nailing  of  the  plank  will  draw  the 
sills  up,  and  if  too  little  there  will  be  uneven  settling.  Next, 
the  planking  B  is  nailed  down.  Unless  these  planks  are  edged 
and  well  dried  they  should  be  battened  water  tight  on  that  part 
of  the  mat  over  which  the  water  will  be  conducted  during  the 
building  of  the  last  half.  It  is  a  good  plan  to  make  this  deck 
of  two  layers  of  1-inch  boards,  breaking  joints  at  edges  and  ends. 
This  makes  the  mat  more  flexible.  The  row  of  sheet  piling  C 
is  driven  as  deep  as  possible  and  a  water-tight  connection  made 
with  the  mat.  The  row  D  is  not  attached  to  the  mat,  and  the 
spaces  usually  left  will  permit  the  seepage  water  to  find  an  outlet 
without  exerting  an  uplift  on  the  mat.  It  is  also  desirable  to 
permit  the  mat  to  settle,  which  it  could  not  do  if  it  were  fastened 
to  the  piling.  The  intermediate  sills  E  run  up  and  down  stream, 
being  placed  a  distance  apart  equal  to  the  distance  between  the 
dam  bents,  so  that  each  bent  will  rest  directly  over  a  sill.  The 
sills  F  run  lengthwise  of  the  dam,  thus  forming,  with  the  sills 
E,  a  series  of  compartments,  each  as  wide  as  the  distance  between 
dam  bents,  and  as  long  as  the  mat.  These  compartments  are 
filled  with  gravel  or  stone,  and  the  top  planks  G  are  then  laid. 
The  top  planks  are  merely  for  the  purpose  of  conducting  the 
water  over  the  mat  without  allowing  it  to  wash  out  the  gravel, 
so  they  need  not  be  edged  or  the  cracks  battened.  Along  the 
up-stream  edge  of  the  mat  is  built  the  breast  wall.  The  posts  H 
are  placed  five  or  six  feet  apart  and  should  be  from  four  to  ten 
feet  in  height,  depending  on  the  height  of  dam.  The  tops  should 
not  come  near  enough  to  the  surface  to  be  struck  by  floating  ice, 
logs,  etc.  The  breast  wall  serves  two  very  important  purposes: 
During  construction  it  is  used  to  shift  the  water  from  one  part 
of  the  mat  to  another,  so  as  to  aid  in  building  the  dam.  By  its 
use  the  water  may  be  raised,  a  plank  at  a  time,  until  the  fill  above 
it  is  completed.  It  also  serves  to  hold  the  fill  over  the  edge  of  the 
mat,  the  only  place  where  the  water  could  possibly  find  an  outlet. 
This  fill  is  made  as  high  as  the  current  going  over  the  breast  wall 
will  permit.  The  breast  wall  is  not  placed  on  top  of  the  plank  G, 
but  on  the  lower  course.  In  this  way  greater  flexibility  is 
obtained  between  the  mat  directly  under  the  dam  and  where  it 


222 


HYDROELECTRIC  PLANTS. 


is  attached  to  the  piling.  Also  a  small  amount  of  fill  can  be 
made  over  the  edge  of  the  mat  without  filling  above  the  top 
level.  The  posts  are  held  by  means  of  rods,  or  may  be  braced. 
The  timbers  used  for  heads  up  to  20  feet  are  8x8  inches,  and  for 
very  low  heads  6x8  inches. 

The  length  of  the  mat  should  be  such  that  the  foot  boards 
will  not  strike  the  breast  wall  in  being  dropped,  and  that  the  down 
stream  edge  of  apron  will  just  come  to  the  edge.  Water  from 
the  overpour  should  never  be  allowed  to  strike  the  mat. 
It  will  be  seen  that  it  is  a  physical  impossibility  for  water 
to  ever  cut  under  such  a  mat.  In  an  experience  with  over  60 
such  mats  the  author  has  never  known  the  water  to  get  under 
one.  Owing  to  cheap  construction  several  have  been  under- 
mined from  below,  but  never  injured  along  the  breast  wall. 


-!* 


S77<7/ 


FIG.  212. 

^Fig.  196,  gives  a  good  idea  of  the  construction  of  such 
mats.  In  this  case  the  water  was  all  turned  through  the 
power  house,  seen  in  the  distance,  and  the  breast  wall  was  filled 
full  depth  at  once.  The  trench  shown  to  the  left  was  to  make 
the  driving  of  the  sheet  piling  more  easy.  Each  alternate  sill 
should  be  drifted  to  the  mud  sills  with  at  least  2 — f  x!4-inch  drift 
spikes.  The  planking  is  done  with  30d  spikes. 

In  the  majority  of  cases  it  is  necessary  to  build  half  of  the  mat 
at  a  time.  During  the  building  of  the  first  half  (or  as  much 
more  than  half  as  possible)  the  water  is  turned  to  the  other  side 
of  the  river,  but  while  building  the  last  half  it  runs  over  the  com- 
pleted portion.  (See  Fig.  212.) 

In  this  case  the  entire  surface  of  the  mat  is  exposed  to  the 


HYDRAULIC  CONSTRUCTION. 


223 


water,  and  if  there  is  any  leakage  it  will  follow  along  the  sills 
toward  the  uncompleted  mat,  when  the  water  is  pumped  out, 
unless  a  cut-off  wall,  A,  is  put  in.  It  will  pay  to  do  a  good  job 
on  this  cut-off.  The  author  has  found  that  a  concrete  wall 
as  shown  at  A  Figs.  212  and  213  is  the  best.  This  wall  is 
built  before  the  mat  is  laid  near  to  it  on  either  side,  and 
should  go  down  to  firm  bottom  if  possible.  The  top  must 
not  be  more  than  an  inch  or  so  above  the  top  of  the  mat, 
and  only  extend  to  the  up  and  down-stream  row  of  piling; 
along  the  top  is  embedded  a  plank  or  timber  to  which 
temporary  planks  may  be  nailed.  These  temporary  planks  are 
tongued  and  grooved  and  keep  out  the  water.  The  mat  simply 
abuts  against  the  wall  and  does  not  project  into  it  at  any  place. 
A  row  of  piling  may  be  used  in  place  of  the  wall. 


FIG.  213. 


The  cost  of  laying  a  mat  is  about  3  cents  per  square  foot, 
including  digging  the  trenches  for  mud  sills,  leveling,  planking, 
etc.,  but  does  not  include  the  fill  above  breast  wall.  Three  kegs 
of  30d  nails  are  required  to  1000  square  feet  of  mat.  A  timber 
mat  requires  from  5J  to  7  square  feet  of  lumber  per  superficial 
square  foot. 

The  dam  and  the  abutments  are  placed  on  the  mat.  The 
dam  may  be  of  the  crib  type  if  desired,  though  commonly  the 
frame  dam  is  used.  It  may,  of  course,  be  fastened  down  to  the 
mat  by  means  of  drifts,  but  this  is  wholly  unnecessary,  as  once 
the  water  pressure  is  on  nothing  could  stir  the  dam.  A  few 
years  ago,  to  demonstrate  to  an  incredulous  city  board  that  the 
dam  would  not  slip  off  the  mat,  a  model  dam  was  built  and 
placed  on  the  slimy  floor  of  an  old  penstock.  The  dam  was  four 
feet  high  and  just  fitted  into  the  penstock,  without  quite  touch- 
ing at  the  ends.  The  water  was  turned  on  all  at  once  and  the 


224  HYDROELECTRIC  PLANTS. 

model  only  slid  one  inch  and  then  settled  solidly  upon  the  floor. 

Figs.  214  and  215  show  dams  of  the  frame  type  and  are  suited 
either  to  place  on  mats  or  solid  rock.  There  should  be  no  mortise 
and  tenon  joints  about  a  dam,  as  experience  has  proved  that 
such  joints  are  the  first  places  to  decay.  A  plain  sawed  butt 
joint  is  all  that  is  necessary,  there  being  no  side,  strains  at  all. 
Four  40d  spikes  are  used  at  each  joint  to  hold  the  parts  in  place. 

The  designing  of  a  frame  gravity  dam  is  a  very  simple 
operation.  Take  the  example  of  a  20-foot  dam  with  5 
feet  of  water  going  over  it.  (Fig.  215.)  First,  assume  the 
slant  of  the  deck  to  be  23°,  and  draw  the  decking.  Then  at 
5-foot  intervals  erect  verticals  to  get  the  depth  or  head 
of  water  at  those  points.  Multiply  the  depth  by  62.5 
to  obtain  the  pressure  per  square  foot  on  the  deck.  Thus, 
at  vertical  (1),  when  the  depth  is  22  feet  the  pressure  is  1375 
pounds  per  square  foot.  Now  the  up-stream  plate  A  must,  in 
most  cases,  be  high  enough  above  the  mat  to  allow  the  passage 
of  the  water  underneath.  This  makes  the  length  of  the  foot 
board0  B  about  six  feet,  and  the  plate  A  will  then  have  to  sustain 
practically  half  the  weight  on  these  foot  boards.  If  the  distance 
between  bents  is  four  feet,  1469X3X4  is  the  part  of  the  pressure 
on  the  foot  boards  held  by  the  plate.  It  will  also  hold  half  the 
weight  on  the  3-foot  span  to  the  next  plate,  which  is  1375X1.5 
X4.  The  sum  of  the  two  is  25,876  pounds.  From  table  (55*) 
an  oak  beam  one  inch  thick  and  10  inches  deep  will  safely  sustain 
a  load  of  2640  pounds,  therefore  a  lOxlO-inch  beam  will  sustain 
26,400  pounds.  At  depth  (2)  the  pressure  per  square  foot  is 
1250  pounds  and  the  area  supported  by  the  plate  C  is  4JX4 
=  17  square  f eet ;  therefore ,  the  load  on  C  is  4JX4.X  1250  =21,250 
pounds,  for  which  an  SxlO-inch  timber  is  found  to  be  right. 
As  it  is  not  best  to  use  a  smaller  timber  than  an  8x8-inch  in  a 
dam  of  this  size,  all  the  remaining  plates  will  be  made  of  SxS-inch 
timbers,  and  they  should  be  spaced  up  and  down  stream  so  that 
the  full  strength  of  the  decking  will  be  utilized.  At  (3)  they 
could  safely  be  four  feet  apart,  and  at  (7)  six  feet,  so  six  feet 
will  be  taken  as  the  maximum  distance  at  the  crest  and  then 
gradually  diminish  the  span  toward  the  toe. 

The  posts,  if  made  of  8x8-inch  timbers,  will  be  many  times 
stronger  than  necessary,  but  a  smaller  size  would  make  the 
pressure  at  the  ends  too  severe.  From  table  (54*)  a  post  six 

*  See  Chapter  IX. 


HYDRAULIC  CONSTRUCTION. 


225 


226 


HYDROELECTRIC  PLANTS. 


HYDRAULIC  CONSTRUCTION.  227 

feet  long  and  8x8  inches  section  will  safely  sustain  41,000 
pounds  for  white  pine,  and  for  oak  about  52,000  pounds.  At  D 
the  lock  block  is  bolted  to  the  sill  with  a  J-inch  bolt.  This 
block  stiffens  the  dam  against  the  horizontal  forces  acting  at 
crest  of  dam,  such  as  ice  expansion. 

The  design  of  the  apron  is  more  important  perhaps,  than  any 
other  part  of  the  dam.  If  the  water  is  given  no  object  to  strike 
against  the  only  way  'the  apron  can  be  injured  is  by  wearing 
out  under  the  friction  of  the  water.  In  this  design  a  curved 
apron,  having  a  crest  formed  to  prevent  the  water  from  falling 
perpendicularly  over  on  to  it,  is  shown.  This  crest  can  be 
covered  with  boiler  iron.  The  curve  is  obtained  by  nailing 
together  segments  made  of  3-inch  plank.  The  straight  part  of 
the  apron  is  made  of  3-inch  white  oak  or  yellow  pine,  and  the 
lower  portion  is  built  up  like  the  crest,  the  segments  all  being 
sawed  to  template  before  placing  on  the  frame  of  the  dam.  The 
only  strain  on  the  timbers  is  that  due  to  the  weight  of  the  water, 
and  when  passing  over  the  apron  this  is  in  a  very  thin  sheet. 
The  segments  of  the  apron  should  be  sawed  so  that  the  grain 
will  run  with  the  current. 

The  foot-boards  B,  are  of  4-inch  plank.  Each  bottom  board 
is  notched  on  one  edge  so  that  it  will  bear  its  part  of  the  pressure. 
If  the  bottom  boards  were  water-tight  no  pressure  would  come 
on  to  the  top  boards  at  all.  Curve  (Fig.  258)  gives  the  thou- 
sands of  feet  of  lumber  in  100  feet  of  dam  similar  to  that  just 
designed. 

Fig.  216  shows  a  gravity  dam,  made  principally  of  steel. 
The  details  of  construction  may  be  worked  out  in  a  great  many 
different  ways,  but  the  design  shown  will  serve  to  illustrate  the 
principle.  The  deck  is  of  tongue  and  grooved  plank,  as  in  the 
timber  dam.  As  the  deck  is  at  all  times  in  direct  contact  with 
the  water  it  is  preserved  from  decay.  The  apron  is  made  of 
segments  as  shown.  If,  for  any  reason,  the  sill  cannot  be  placed 
under  water,  another  channel  should  be  used  in  its  place,  forming, 
with  the  one  shown,  a  box  girder. 

Fig.  220  shows  a  design  for  a  concrete-steel  dam.  This  form 
of  dam  is  the  combination  of  all  that  is  good  in  both  the  timber 
gravity  dam  and  the  concrete  dam.  The  use  of  the  steel  re- 
inforcing makes  the  design  as  certain  as  it  would  be  for  an  all- 
steel  dam.  The  compressive  strength  of  the  concrete  is  used 


228 


HYDROELECTRIC  PLANTS. 


HYDRAULIC  CONSTRUCTION. 


229 


to  the  fullest  extent,  but  all  tensional  stress  is  thrown  upon  the 
steel.  The  steel  being  embedded  in  the  concrete  will  not  rust, 
and  therefore  the  permanence  of  the  structure  is  secured. 

For  rock  bottom  the  apron  may  be  omitted  (Figs.  218  and  219). 


The  passageway  is  for  the  free  admission  of  air  to  the  interior 
and  to  permit  inspection. 

There  are  certain  conditions  under  which  even  a  concrete- 
steel  dam  will  fail   to   give  perfect  satisfaction.     Thus,  if  the 


230 


HYDROELECTRIC  PLANTS. 


bottom  yields  ever  so  little,  the  dam  will  crack.  The  steel  will 
hold  it  together,  but  leaks  will  start,  which,  in  time,  will  cause 
damage  and  loss  of  power.  Again,  such  a  dam  must  necessarily 
be  constructed  entirely  in  place  in  the  river  bed,  which  means 
more  or  less  risk  from  floods  during  the  building. 


v~ZL 


Designed  for  the 
Roberts  & 
Abbott  Co. 


FIG.  219. — Reinforced  gravity  dam. 

The  design  (Fig.  220)  shows  a  dam  that  is  composed  of  indi- 
vidual reinforced  members,  each  of  which  is  built  on  shore,  and 
thoroughly  tested  and  seasoned  before  placing  in  the  dam.  The 
deck  is  made  up  of  these  segments  C,  and  the  apron  deck  is  .nade 
of  similar  segments,  the  only  difference  being  that  the  apror 


HYDRAULIC  CONSTRUCTION. 


231 


segments  are  of  less  depth  and  have  more  anchor  bolts.  Each 
segment  has  recesses,  F,  moulded  along  the  sides,  so  that  when 
cemented  between,  as  G,  the  whole  is  bound  together.  Each 
segment  is  a  beam  eight  inches  deep  and  12  inches  wide,  in  the 


dam  shown,  and  as  long  as  the  distance  between  bents,  each 
sustains  eight  times  the  actual  pressure  per  square  foot,,  and 
may  be  designed  from  tables  in  Chapter  IV. 


//  YDR A  ULIC  CONS  TR  UCTION. 


233 


234 


HYDROELECTRIC  PLANTS. 


l 


HYDRAULIC  CONSTRUCTION. 


235 


236  HYDROELECTRIC  PLANTS. 

Referring  to  Table  XXIXa,  page  121,  we  find  that  the 
segments  near  the  toe  of  the  dam  should  be  10  inches  deep  and 
be  reinforced  with  1.31  square  inches  of  mild  steel  to  sustain  the 
load.  The  first  segment  supports  three  feet  of  the  the  foot 
boards,  or  3X8  =  24  square  feet  of  surface;  therefore,  24X1000 
=  24,000  pounds  is  the  pressure  upon  it.  For  this  beam  of 
14-inch  depth  two  inches  of  steel  are  required.  At  each  end 
of  the  segments  is  molded  a  half  recess  to  permit  of  bolting  to 
the  deck  and  apron  plate.  When  the  segments  are  all  in  place 
on  the  dam  a  rich  cement-sand  mortar  is  filled  in  between, 
making  the  joints  water  tight.  Now  as  these  segments  only 
run  from  one  bent  to  the  next,  it  is  evident  that  one  bent  could 
sink  a  good  deal  without  impairing  the  strength  of  the  dam. 
Also  if  the  deck  warps,  the  only  place  a  crack  would  occur  would 
be  between  the  segments  and  not  across  them,  where  the  rein- 
forcing is. 

In  a  dam  of  the  size  shown  (Fig.  220),  the  sill  A  is  made  all 
in  one  piece,  but  for  higher  dams  it  may  be  made  in  more  pieces. 
Where  each  post  comes,  a  steel  plate  E  is  molded.  The  four 
holes  have  the  same  spacing  as  the  reinforcing  rods  in  the  posts, 
so  that  when  the  post  is  set  up  the  rods  slip  onto  them.  At  H 
a  plate  is  molded  into  A ,  so  that  the  bolts  connecting  it  with  the 
sill  will  have  greater  shearing  value.  The  holes  for  these  bolts 
are  cored  into  the  plate.  The  apron  plate  is  made  in  the  same 
way,  a  number  of  anchor  bolts  being  molded  in,  to  hold  the 
apron  segments.  The  sill  is  10x1 0-inch  and  reinforced  with 
Ix3-inch  bars.  The  dimensions  of  the  posts  are  obtained  from 
the  formula:  Safe  Load  =  350  (area  of  concrete +15 X area  of 
reinforcing  steel). 

This  dam  may  be  placed  upon  a  timber  mat  the  same  as  a 
timber  dam.  Gravel  should  be  placed  on  the  deck  so  that  if  a 
crack  should  occur  leakage  will  be  prevented. 

WING    DAMS. 

On  navigable  rivers,  wing  dams  are  sometimes  built  to  avoid 
obstructing  navigation.  These  dams  are  run  part  way  across 
the  river  and  frequently  quite  a  distance  up  the  stream.  The 
head  thus  acquired  is  necessarily  low,  but  usually  in  such  cases 
there  is  plenty  of  water.  At  Rock  Island,  111.;  there  is  a  very 
large  power  created  by  a  wing  dam  and  used  by  the  United  States 
Government  at  its  arsenal. 


HYDRAULIC  CONSTRUCTION. 


237 


The  wing  dam  is  built  in  the  same  way  as  others  described 
except  at  the  end  which  receives  the  full  force  of  the  current. 
At  this  point  every  precaution  must  be  taken  to  provide  against 
undermining.     The  pier  A,  Fig.  225,  is  built  first,  a  coffer  being 
built  so  that  the  bottom  of  the  river  may  be  excavated. 


FIG.  225. 

The  foundation  of  this  pier  must  go  down  below  the  level  of 
possible  wash.  Having  built  a  safe  end  the  building  of  the  dam 
possesses  no  unusual  difficulties. 

BOW    DAMS. 

Dams,  especially  masonry  dams,  are  often  bowed  up  stream, 
as  shown  in  Fig.  226,  in  an  exaggerated  form.  The  idea  is  to 
get  the  strength  of  an  arch.  When  the  ends  of  vertical  faced 
masonry  dams  are  given  a  secure  anchorage,  as  in  Fig.  226, 
there  is  no  doubt  but  that  a  great  increase  in  strength  is  secured, 
by  the  arch,  but  the  ends  must  make  an  angle  with  the  stream 
such  that  a  line  CD,  coinciding  with  them,  passes  inside  the 
center  of  curvature.  The  water  pressure,  being  perpendicu1ar 
to  the  surface  at  all  points,  presses  every  part  towards  the  center 


238 


HYDROELECTRIC  PLANTS. 


of  curvature,  and  if  the  ends  are  given  a  less  slant,  as  A  B,  the 
pressure  at  P  tends  to  shove  the  end  away  from  the  cliffs  and 
the  dam  is  no  stronger  than  if  built  straight.  The  author  knows 
of  two  bowed  masonry  dams,  each  of  which  failed  at  both  ends. 
For  timber,  or  gravity  dams  of  any  material,  the  bow  adds 
no  degree  of  safety.  The  old-style  crib  dam,  unless  very  short, 
would  gain  little  by  the  arching,  as  it  would  fail,  due  to  local 
weakness  at  some  one  point,  and  disintegrate  without  giving  an 


FIG.  226. 

end  thrust.  The  gravity  dam  depends  on  the  vertical  water 
pressure  to  hold  it  in  place,  therefore  the  arch  would  add 
nothing  to  its  security. 

MASONRY    DAMS. 

The  search  for  permanence  has  developed  the  masonry  dam. 
Its  great  first  cost  would  have  made  its  use  impossible  had  there 
not  been  a  strong  prejudice  against  all  other  forms.  The  feeling 
of  security  given  by  the  use  of  masonry  often  made  a  proper 
disposition  of  the  materials  a  secondary  consideration,  with  the 
result  that  the  list  of  masonry  dam  casualties  contain  almost 
as  many  failures  as  that  of  timber  dams. 

With  the  passing  of  the  forest  and  the  decreasing  cost  of 
concrete,  however,  it  becomes  more  and  more  important  that 
we  perfect  the  masonry  or  concrete  dam. 

Assuming  that  the  concrete  or  masonry  is  properly  laid, 
there  are  eight  prime  factors  which  must  be  determined  and 
provided  for  before  the  actual  work  of  construction  begins: 


//  YDRA  ULIC  CONSTR UCTION. 


239 


1.  Wall  being  sheared  by  the  horizontal  push  of  the  water. 

2.  Undermining  below  the  dam,  due  to  weak  apron. 

3.  Resistance  to  sliding  on  its  base. 

4.  Effect  of  vacuums. 

5.  Effect  of  flotation  on  the  weight  of  materials. 

6.  Effect  of  ice  expansion. 

7.  Liability  of  seepage  under  the  dam. 

8.  Weakness  of  green  concrete  or  masonry. 

To  convince  the  reader  that  it  is  worth  while  to  study  the 
above  points  well  before  indulging  in  hasty  construction,  the 
cross-sections  of  a  few  masonry  or  concrete  dams  which  have 
failed,  are  given  in  Figs.  227  and  228,  these  costing  millions  of 


FIGS.  -227,    228. 

dollars  and  a  great  many  lives.  The  cause  of  these  failures  may 
be  found  among  the  above  eight  factors,  and  the  probable  factors 
which  caused  the  failure  have  been  indicated  on  each  section. 

The  author  contends  that  the  cause  of  so  many  disasters  is 
because  the  factors  4,  5,  6,  7  and  8  have  not  been  understood, 
and  by  merely  building  to  oppose  the  hydraulic  pressure,  instead 
of  turning  them  in  to.  factors  of  safety. 

By  referring  to  these  sections  it  will  be  seen  that  without  an 
exception  the  up-stream  face  of  the  dams  are  vertical,  or  prac- 
tically so,  and  that  all  are  apparently  of  heavy  proportions, 
when  the  water  pressures  alone  are  considered.  In  discussing 
the  above  eight  factors  it  must  be  borne  in  mind  that  there  are 


240 


HYDROELECTRIC  PLANTS. 


but  two  forces,  the  amount  of  which  can  be  figured  with  any 
degree  of  accuracy.  These  are  the  hydraulic  pressure  and  the 
crushing  strength  of  the  masonry.  It  is  an  undisputed  fact  that 
the  tensile  strength  of  masonry  or  concrete  is  so  uncertain  that 
it  can  not  be  relied  upon  at  all.  Also  the  shearing  strength  is 
unreliable.  The  weight  of  the  material  is  a  quantity  which  is 
equally  difficult  to  compute,  owing  to  the  factor  of  flotation- 
Of  course,  it  is  at  once  apparent  that  the  portion  of  the  dam 
which  is  below  the  surface  of  tail  water  is  lifted  up  by  the  amount 
of  the  weight  of  the  displaced  water,  and  that  this  lifting  effect 
is  increased  by 'the  backwater  caused  by  floods. 

It  has  been  contended  that  the  water  which  soaked  into  the 
masonry  owing  to  the  hydraulic  pressure  did  not  affect  the  weight 
of  the  material  thus  soaked,  but  lately  leading  engineers  are 
taking  the  stand  that  the  weight  is  very  materially  affected, 
though  as  to  just  what  extent  they  are  still  at  variance.  This 
loss  in  the  effective  weight  of  the  material  the  author  calls  the 
factor  of  flotation,  as  the  tendency  is  to  float  the  masonry,  and 
has  demonstrated  to  his  own  satisfaction  that  it  is  not  safe  to 
figure  the  effective  weight  of  the  affected  masonry  at  more  than 
two-thirds  its  actual  weight. 

In  the  following  table  is  given  the  amounts  of  water  which  a 
cubic  foot  of  sand  and  some  common  rocks  will  absorb: 

TABLE  XXXVII. 


Material. 

Water  absorbed 
per  cubic  foot. 

Material. 

Water  absorbed 
per  cubic  foot. 

Sand 

Quarts. 
10 

Dolomite    ' 

Quarts. 
1  to  10 

2  to  6 

Chalk 

g 

Triassic  sandstone 

4 

Granite  

1/100  to  1 

Trenton  limestone  

JtolJ 

Bearing  in  mind  these  points,  it  will  be  seen  how  very  uncertain 
is  the  material  which  has  been  looked  upon  in  the  past  as  the 
most  trustworthy  agent  to  resist  the  hydraulic  forces.  Its  one 
factor  upon  which  reliance  may  be  placed  (the  crushing  strength) 
has  never  been  made  use  of  in  the  past,  as  all  masonry  dams 
which  have  failed,  however  scant  their  dimensions  may  have 


HYDRAULIC  CONSTRUCTION.  241 

been,  were  absolutely  safe  against  crushing.  This  is  because  the 
structures  were  built  so  weak  in  other  ways  that  the  limit  of  the 
crushing  strength  could  not  possibly  be  reached  before  there 
was  a  wash-out  due  to  some  other  cause. 

We  will  now  take  up  the  eight  factors  in  their  order  and  con- 
sider their  importance  in  the  design  of  dams: 

1.  If  the  dam  should  give  way  at  G  D,  Fig.  232,  owing  to  the 
horizontal  down-stream  push  of  the   hydraulic  pressure,  it  is 
sheared  at   that  point.     Even   an   approximate   value   for  the 
shearing  strength  is  impossible  to  predetermine,  as  it  depends 
on  variables,  such  as  evenness  of  mixing  the  mortar  or  concrete; 
parting  lines  formed  between  bodies  of  the  materials  laid^at 
different  times;  strains  set  up  in  the  materials,  owing  to  uneven 
setting,  etc. 

2.  One  of  the  most  common  causes  of  disaster  is  due  to  the 
dam  being  undermined  on  the  down-stream  edge  of  the  structure, 
and  to  the  sucking  force  of  vacuums.     To  prevent  this  a  massive 
extension  mat  must  be  provided.      (See  design  on  page  234). 

3.  Referring  to  the  sections  of  the  above  dams  it  will  be  seen 
that  all  the  pressure  is  directly  down  stream,   because  it  is  a  well 
known  law  that  water  pressure  is  always  perpendicular  to  the 
exposed  surface.     Therefore  the  only  thing  to  hold  these  dams 
in  place  is  the  friction  between  the  bed  of  the  stream   and  the 
dam.     The  Austin  dam  is  a  very  noteworthy  example  of  a  dam 
which  failed  by  sliding  on  its  base.     A  large  section  slid  bodily 
down  stream  and  still  stands  erect,  several  hundred  feet  below 
its  original  position.     Of  course,  the  heavier  the  materials,  the 
greater  the  friction.      The   crushing  strength  of  the  masonry, 
however,  does  not  enter  into  consideration. 

4.  In  considering  the  fourth  factor  the  reader  is  referred  to 
the  result  of  the  Cornell  experiments,  given  on  page   14.     These 
experiments  prove  that,  for  even  a  small  fall  and  overpour,  a 
powerful  vacuum  is  formed.     In  the  case  of  the  eight-foot  dam 
it  had  to  sustain  the  equivalent  of  five  feet  of  head  in  addition 
to  the  eight  feet,  or  over  half  again  as  much.     This  means  312 
pounds  per  square  foot  of  surface.     Where  the   dam  is  from 
40  to  100  feet  high  and  the  sheet  of  water  flowing  over  the  apron 
is  six  or  eight  feet  thick,  the  vacuum  must  be  almost  perfect. 
It  has  been  found  that  the  vacuum  adds  fully  1000  pounds  pe'r 
square  foot  to  the  pressure  on  the  dam  where  the  dam  is  20  or  30 


242 


HYDROELECTRIC  PLANTS. 


feet  high  and  the  sheet  four  feet  or  more  thick.  The  presence  of 
a  vacuum  can  be  qualitatively  demonstrated  by  noting  the  in- 
rush of  air  at  the  inlets  provided  in  dams  for  the  relief  of  the 
vacuum.  The  Columbus,  Anderson  and  the  Upper  and  Lower 
Tallassee  dams  all  failed  within  a  day  or  two  of  each  other, 
and  in  each  case  the  hydraulic  pressure  (owing  to  the  back- 
water) was  less  than  at  any  other  time  in  the  history  of  the  dam. 
Then  why  did  they  fail  ?  Simply  because  of  the  terrible  vacuum 
pressure  and  the  floating  effect  produced  by  the  increased  back- 
water below  the  dam. 

In  order  to  more  clearly  demonstrate  the  action  of  vacuums, 
the  following  reasoning  is  given:    Referring  to  Fig.  229,  the  sec- 


FIG.  229. 


tion  of  the  overflowing  water  is  similar  to  that  of  the  dam. 
Now  there  are  two  fundamental  laws  of  motion  which  we  must 
accept  as  being  correct. 

1.  A  body  under  motion  will  continue  so  unless  acted  on  by 
some  external  force. 

2.  Action   and   reaction   are   equal   and   oppositely   directed. 
The  action  of  the  air  pressure  when  a  vacuum  is  formed  is  to 
deflect  the  mass  of  falling  water  from  its  normal  path,  as  shown 
by  the  dotted  lines.     Of  course  there  can  be  no  question  but  that 
to  deflect  tons  of  rapidly  falling  water  force  is  required.     This 
force  shows  itself  by  the  difference  in  elevation  of  the  water 
behind  the  pour,  and  that  below,  as  the  levels  a  and  b.     Accord- 
ing to  the  second  law  there  must  be  some  reaction  to  the  air 
pressure  on  the  overflow.     Suppose  Fig.  229  to  take  more  simple 
form,  as  in  Fig.  230,  the  impended  water  not  being  considered. 


HYDRAULIC  CONSTRUCTION.  243 

Now  the  water  between  the  overflow  and  the  dam  is  held  to  the 
level  a,  by  the  partial  vacuum  V.  In  other  words,  the  water  is 
sucked  up  in  between  the  dam  and  the  overpour,  creating  a  suction 
on,  not  only  the  wall  of  water  on  the  right,  but  also  on  the  wall 
of  masonry  on  the  left.  Can  there  be  any  question  on  this  point? 
Mr.  Frizell,  in  his  very  excellent  treatise  on  hydraulics,  says, 
"  Its  greatest  possible  deleterious  effect  would  be  to  press  the 
stream  against  the  down  stream  face  of  the  dam,"  and  claims 
that  the  vacuum  tends  to  sustain  the  dam.  Of  course  this  view 
is  faulty,  as  it  does  not  consider  the  reaction  on  the  pond-side 
of  the  dam.  Filling  the  pond  above  the  dam  does  not  change 
the  above  reasoning,  as  the  air  pressure  is  perfectly  transmitted 
through  the  imponded  water. 

The  water  and  the  wall  tend  to  be  sucked  into  the  vacuum, 
and  to  resist  this  suction  a  certain  factor  of  safety  must  be 
allowed. 


FIG.  230. 

"  Suction  is  the  act  of  exhausting  air  from  a  cavity,  but  it  acts 
upon  the  air  within  the  cavity,  not  upon  the  walls  of  the  cavity, 
nor  upon  any  substance  heavier  than  the  air;  a  piece  of  paper 
upon  the  floor  of  the  cavity  would  not  be  disturbed  by  the 
suction.  Suction  is  the  primary  cause  and  vacuum  is  the  effect. 
The  breaking  of  the  walls  of  the  cavity  is  the  effect  of  a  secondary 
cause — -atmospheric  pressure — forcing  in  the  walls  to  fill  the 
vacuum. 

Its  action  may  be  better  understood  from  the  following 
illustration:  A  piece  of  pliable  leather  having  a  cord  attached 
to  its  center,  when  saturated  with  water  and  pressed  upon  a 
stone,  adheres  with  such  force  that  in  many  instaces  it  is  possible 
to  lift  the  stone.  The  pull  on  the  cord  reduces  the  atmospheric 
pressure  on  top  of  the  stone,  and  in  cases  where  the  stone  is  not 
heavier  than  the  total  pressure  on  the  leather  it  is  possible  to 
reduce  the  pressure  on  top  of  the  stone  to  such  an  extent  that 
the  atmospheric  pressure  from  below  will  lift  the  stone. 


244  HYDROELECTRIC  PLANTS. 

The  operation  of  this  familiar  experiment  is  precisely  the 
same  as  that  of  vacuum  suction  on  dams.  The  sheet  of  water 
is  represented  by  the  piece  of  pliable  leather,  the  dam  by  the 
stone  against  which  the  sheet  is  pressed,  and  the  projectile  force 
of  the  sheet  by  the  pull  upon  the  cord. 

If,  in  the  experiment,  the  atmospheric  pressure  is  greater  than 
the  weight  of  the  stone,  the  stone  will  be  lifted  and  no  vacuum 
formed,  and  so  the  dam  may  receive  a  pull  equal  to  the  projectile 
force  of  the  sheet,  even  though  the  over-pour  does  not  leap  away 
from  the  apron  and,  without  causing  a  vacuum,  develop  an 
unseen,  unsuspected  force,  which  may  have  the  power  to  destroy 
the  dam. 

Since  it  is  evident  that  suction  brings  into  action  a  secondary 
force  against  the  outside  face  of  the  cavity  or  wall  only,  we  are 
driven  to  the  conclusion  that  the  facings  on  the  lower  half  of 
aprons  are  not  displaced  by  suction. 

The  more  probable  cause  of  the  defacement  of  aprons  is  found 
in  a  deficient  resisting  power  of  the  masonry,  the  erosion  of 
weak  mortar  from  poorly-constructed  joints,  and  the  develop- 
ment of  vibrations  caused  by  great  columns  of  water  pounding 
upon  the  facings  with  a  force  of  many  thousands  of  tons.  This 
theory  is  the  more  probable  since  the  facings  are  not  torn  off 
at  points  above  the  lower  half  of  the  apron  where  vacuums  do 
occur,  but  are  torn  off  at  a  point  where,  in  all  probability,  they 
do  not  occur."* 

Now  as  to  the  amount  of  this  air  pressure:  At  first  thought  it 
would  seem  that  the  effective  pressure  would  only  be  figured  as 
pressing  the  dam  from  the  crest  down  to  the  surface  of  the  water 
a,  Fig.  231,  but  this  is  not  so.  Referring  to  Fig.  231,  the  column 
of  water  behind  the  over-pour  caused  by  the  vacuum  reacts  on 
the  dam,  tending  to  neutralize  the  vacuum  pressure.  The 
pressure  against  the  dam  considering  only  the  vacuum  pressure 
and  that  due  to  the  level  E  D,  at  the  water  level  C  D  the 
pressure  is  zero,  but  at  level  A  B  and  H  I  it  equals  the 
pressure  due  to  the  level  E  D  and  therefore  equals  the  vacuum 
pressure.  The  line  E  A  H  therefore  is  the  line  of  pressures 
at  any  point  along  E  F.  due  to  the  backwater  against  the  dam, 
and  the  line  C  F  is  the  line  of  vacuum  pressure.  As  the 


*E.  R.  Beardsley. 


H YDRA  ULIC  CONSTR UCTIOX. 


245 


air  pressure  acts  against  the  up-stream  face  of  the  dam, 
through  the  emponded  water,  it  must  be  perpendicular  to 
that  surface  of  the  dam,  and  will  be  uniformly  distributed 
along  the  face.  We  may,  therefore,  represent  this  vacuum 
by  the  line  C'  G'  parallel  to  this  face  and  at  a  distance 
from  it  equal  to  the  vacuum  pressure.  The  line  C'  Ff  is  CF 
transferred.  Now  the  center  of  gravity  of  this  shaded,  area 
Ff  E'  Gr  C',  which  represents  the  entire  vacuum  pressure,  may 
be  found  and  the  whole  pressure  considered  as  acting  at  that 
point,  and  tending  to  slide  or  overturn  the  dam. 

The  amount  of  vacuum  pressure  for  any  particular  dam  is 
very  difficult  to  determine,  owing  to  the  lack  of  data  on  the  sub- 
ject. The  author  has  made  the  following  experiments  with 
dams  fitted  with  air  inlets: 


FIG.  231. 

A~dam  565  feet  long,  with  a  total  head  six  feet,  and  a  head 
over  the  crest  of  three  feet,  showed  a  vacuum  pressure  of  three 
feet  of  water  or  1 . 31  pounds  per  square  inch ;  a  dam  300  feet  long, 
with  a  total  head  of  12  feet,  and  a  head  over  the  crest  of  30  inches, 
showed  a  vacuum  of  three  feet  of  water  or  1 . 31  pounds  per  square 
inch;  a  dam  275  feet,  with  a  total  head  of  30  feet,  and  a  head 
over  the  crest  of  four  feet,  showed  a  vacuum  of  14  feet  of  water 
or  six  pounds  per  square  inch.  At  Cornell  a  weir  [six  feet  high, 
with  18  inches  of  water,  showed  a  vacuum  pressure  of  two  feet  of 
water  or  0 . 86  pounds  per  square  inch ;  and  a  dam  eight  feet 
high,  with  two  feet  of  water,  showed  a  vacuum  of  five  feet  of 
water  or  2. 16  pounds  per  square  inch.  From  these  examples  a 
fair  guess  may  be  made  as  to  the  probable  pressure  due  to 
vacuums. 


246  HYDROELECTRIC  PLANTS. 

One  of  the  results  of  the  formation  of  the  vacuum  is  to  set 
up  vibrations  which  may  seriously  affect  the  stability  of  the 
structure.  Water  falling  perpendicularly  into  the  river  bed  or 
upon  the  apron,  gives  a  series  of  rapid  blows,  keeping  the  entire 
structure  in  a  tremulous  condition.  A  body  placed  on  t'he  floor 
may  be  easily  moved  if  the  floor  is  vibrated.  Now  add  to  the 
effect  .of  these  constant  vibrations,  the  heavy  rhythmic  vibration 
caused  by  the  vacuum,  and  the  conditions  are  perfect  for  the 
down-stream  movement  of  the  dam.  When  the  overpour  is  not 
too  heavy  the  vacuum  forms  more  or  less  perfectly  until  the 
sheet  of  water  can  resist  the  inward  pressure  of 'the  air  no  longer, 
when  it  breaks  through  the  sheet,  thus  restoring  the  equilibrium. 
This  process  is  repeated  with  great  regularity  and  results  in  an 
intense  horizontal  push  and  pull  on  the  dam.  If  the  vacuum 


inlets  are  too  small,  this  action  takes  place,  causing  a  puffing 
noise,  similar  to  a  locomotive  pulling  a  heavy  train  up  hill. 

5.  It  will  at  once  be  apparent  that  that  portion  of  the  dam 
which  is  entirely  below  tail  water  (see  Fig.  232)  is  floated  up 
with  a  force  equal  to  the  weight  of  the  displaced  water,  but  it 
will  possibly  require  a  little  study  before  the  reader  will  under- 
stand how  the  water  which  seeps  into  the  solid  masonry  can 
cause  a  diminution  of  weight  in  the  affected  portions.  One  of 
the  most  widely  known  and  popular  experiments  to  illustrate 
the  action  of  water  pressure  is  the  bursting  of  a  stout  keg  by 
means  of  a  high  but  thread-like  column  of  water.  This  is  the 
action  which  takes  place  through  the  finest  seam  of  the  most 
minute  interstices  and  exerts  a  lifting  or  floating  effect  on  the 
particles  which  go  to  make  up  the  mass  of  the  structure.  Re- 


HYDRAULIC  CONSTRUCTION.  247 

f erring  to  the  sketch  (Fig.  232)  all  that  masonry  on  the  up-stream 
side  of  the  line  D  C  will  be  affected  in  this  way,  and  there  is  such 
a  small  amount  of  dam  left  unaffected  that  the  only  safe  way 
is  to  suppose  the  entire  structure  as  affected.  A  fairly  safe 
method  is  to  figure  the  mass  of  the  dam  above  tail  water  as  losing 
one-third  its  weight,  and  that  below  tail  water  as  losing  62 
pounds  per  cubic  foot. 

Mr.  J.  B.  Francis  held  that  solid  concrete  deposited  on  bed 
rock  would  be  lifted  or  floated,  and  to  prove  this,  placed  a  pipe 
provided  with  a  pressure  gauge,  in  the  concrete  of  a  dam  and 
found  that  the  gauge  registered  the  full  pressure. 

6.  Ice  expansion,  the  sixth  factor,  becomes,  in  our  northern 
climate,  a  most  deadly  foe  to  all  dams,  and  especially  to  masonry 
dams.  The  co-efficient  of  ice  expansion  is  nine-tenths  of  an  inch  to 
the  100  feet,  and  a  sheet  of  ice  one  mile  long  will  expand  nearly 
four  feet.  It  is  evident  that  dams  do  not  receive  all  this  expansion. 
If  they  did  the  first  severe  winter  would  destroy  them.  A  large 
per  cent,  is  already  expanded  when  the  sheet  is  first  attached 
to  the  dam,  but  the  expansion  will  be  continued  as  long  as  severe 
weather  lasts. 

The  following  is  taken  from  the  Architect  and  Building  .News: 

'  A  short  railway  was  once  built  in  the  Province  of  Ontario 
which  crossed  a  fresh- water  pond,  known  as  Rice  Lake,  by  a 
bridge  two  and  one-half  miles  long.  The  bridge  was  mostly  corn- 
composed  of  trestle-work,  very  strongly  built,  with  uprights 
driven  in  hard  bottom  and  thoroughly  braced.  The  middle 
portion,  over  the  deepest  part  of  the  lake,  was  composed  of 
trusses  eighty  feet  in  span,  supported  by  piers  measuring  12x24 
feet  and  filled  with  stone.  Early  in  the  first  winter  after  the 
bridge  was  built  the  lake  froze  over  to  a  depth  of  about  seven 
inches.  Before  snow  came  to  protect  the  ice,  the  weather 
moderated,  the  sun  shone  out  brightly,  the  ice  expanded,  and 
in  a  few  minutes  the  bridge  was  in  ruins  its  whole  length,  the 
trestles  being  pushed  over  in  the  direction  of  the  principal 
expansion. 

Afterwards  the  trestles  were  repaired  and  filled  in  with 
gravel,  the  top  of  which  is  eight  feet  above  the  level  of  the  water, 
yet  the  expansion  of  ice  during  sunny  days  is  so  great  that  it 
frequently  creeps  up  the  embankment,  and,  by  successive  move- 
ments, is  pushed  upon  the  rails." 


248  HYDROELECTRIC  PLANTS. 

The  extent  of  the  lake  is  not  given,  but  with  an  open  ice  field 
of  from  three  to  four  miles,  and  all  the  conditions  favorable,  the 
expansion  would  be  as  stated.  Many  instances  have  been  known 
on  lakes  and  rivers,  where,  under  the  enormous  pressure,  acres 
of  ice  have  been  hurled  into  the-  air  as  if  by  an  explosion  of  dyna- 
mite. An  instance  of  this  kind  came  under  the  writer's  obser- 
vation a  few  years  since,  on  the  Kankakee  River,  Illinois,  at  the 
mouth  of  Baker  Creek. 

The  expansive  power  of  ice  is  plainly  shown  along  the  shores 
of  the  small  northern  lakes,  more  especially  those  having  firm 
bluffs  on  one  side  and  low,  marshy  lands  on  the  opposite  side, 
which  receive  the  full  force  of  the  expansion,  and  which  after 
many  years  of  repeated  action  have  pushed  inland  the  frozen 
earth  of  the  shore  up  into  parallel  windrows,  dykes  or  moraines 
from  one  to  several  feet  in  height. 

A  singular  phenomenon  attending  expansion  is  that  it  is 
greatest  when  the  sun  comes  out  and  shines  upon  the  ice  while 
freezing.  Short  dams  suffer  less  than  long  ones,  because  the 
abutments  and  banks  offer  great  resistance,  and  expansion  is 
thrown  in  the  direction  of  least  resistance.  If  the  dam  is  long, 
the  shore  protection  is  diminished  and  its  central  portions  more 
exposed.  For  this  reason  the  dam  is  rarely  moved  at  the  abut- 
ments, but  always  at  the  center,  with  decreasing  ratio  towards 
the  ends. 

If  the  dam  is  on  rock  bottom  and  bolted  down,  however  fast, 
the  repeated  strain,  winter  after  winter,  tear  it  loose  from  its 
fastenings.  If  built  on  pilings,  the  movement  is  imparted  to 
them,  loosening  the  foundations,  disturbing  the  general  solidity 
of  the  structure,  causing  leakage  and  assisting  in  the  work  of 
general  dissolution. 

The  only  way  the  vertical  faced  concrete  dam  can  be  built 
to  be  safe  against  ice  expansion,  is  to  give  it  enough  strength 
to  actually  crush  the  ice  against  its  up-stream  face.  Otherwise 
the  ice  will  crush  the  dam,  as  there  is  no  give  and  take  to  masonry. 
Trautwine  gives  12  to  14  tons  per  square  foot  as  the  compressive 
strength  of  ice.  This  means  that  if  a  field  of  12-inch  ice  gets  a 
grip  on  to  the  crest  of  the  dam  it  can  push  it  with  a  force  of  from 
12  to  14  tons  for  each  foot  of  the  length  of  the  dam. 

7^ ,  Seepage  exists  to  a  certain  extent  under  all  dams,  and 
while  it  does  not  always  indicate  a  weakness  may  prove  to  be 


HYDRAULIC  CONSTRUCTION.  249 

a  destructive  factor.  If  the  resistance  to  the  escape  of  the  water 
below  the  dam  at  E  Fig.  232,  is  greater  than  that  to  its  entrance 
under  the  dam  at  F,  there  will  be  a  back  pressure  created  in 
direct  proportion  to  this  difference.  If  in  Fig.  232  we  suppose 
the  water  has  free  access  under  the  dam  as  shown  by  the  double 
shaded  portion,  then  the  whole  bottom  area  of  the  dam  will  be 
lifted  up  with  a  pressure  due  to  the  head  of  water  H  and  the  dam 
floated  out  of  position.  Therefore,  the  up-stream  toe  of  th3 
dam  must  be  made  more  nearly  water-tight  than  the  down- 
stream edge.  In  fact,  drains  should  be  placed  under  the  dam 
to  conduct  away  the  water  which  does  seep  through  the  toe 
at  F.  Fig.  237,  shows  a  dam  of  excellent  design  with  the 
cutoff  duct  a  to  catch  the  seepage  and  the  seepage  trench  b  to 
make  the  toe  as  tight  as  possible.  The  seep  holes  c  need  be  only 
about  six  or  eight  inches  in  diameter  and  about  10  feet  be- 
tween centers  lengthwise  of  the  dam.  AVith  this  design  the 
effect  of  vacuum  is  allowed  for  and  the  dam  allowed  to  rest  with 
all  possible  weight  upon  the  foundation. 

8.  The  eighth  factor  we  believe  to  be  a  very  important  one. 
The  time  taken  to  complete  a  heavy  masonry  dam  varies  from 
two  to  five  years.  To  hasten  the  construction,  large  quantities 
of  masonry  or  concrete  are  laid  each  season,  with  the  result  that 
the  interior  of  the  dam  does  not  get  a  chance  to  dry  out,  and 
hence  has  very  little  strength.  However,  it  is  rushed  to  comple- 
tion late  in  the  season  and  is  compelled  to  withstand  whatever 
floods  may  come  its  way. 

If  there  are  no  floods,  well  and  good;  but  if,  as  in  the  case  of 
the  Cloumbus,  Anderson,  Upper  Tallassee  and  Lower  Tallassee 
dams,  the  floods  come  at  once,  the  dams  are  in  great  danger  of 
destruction.  The  four  above-named  dams  were  new  dams,  but 
all  were  destroyed  by  the  same  flood. 

In  Fig.  233  we  have  attempted  to  show  graphically  the  propor- 
tions of  the  three  great  agents  of  destruction — water  pressure, 
ice  expansion  and  vacuum.  Of  course,  the  dam  does  not  have 
to  be  of  such  great  proportions,  as,  fortunately,  when  the  ice  can 
fasten  to  a  dam  there  would  be  no  vacuums,  there  being  so  much 
water  that  the  ice  could  not  fasten  to  the  dam;  but  the  sketch 
will  show  the  importance  of  each  of  these  factors.  Each  section 
is  completed  without  a  factor  of  safety  and  shows  a  dam  just 
ready  to  be  overturned  by  the  particular  force.  In  calculating 


250 


HYDROELECTRIC  PLANTS. 


the  ice  expansion,  the  very  low  value  of  8000  pounds  pressure 
per  foot  of  dam  has  been  taken.  Trautwine  gives  24,000. 
The  vacuum  pressure  has  been  taken  as  625  pounds  per  square 
foot  of  surface  exposed  and  the  exposed  surface  called  the  area 
10  feet  below  crest  of  dam. 

However  well  designed  a  vertical  faced  masonry  or  concrete 
dam  may  be,  yet  we  must  acknowledge  that  it  is  in  the  nature 
of  a  dangerous  experiment.  Every  great  masonry  dam  that 
was  ever  built  has  called  forth  heated  discussions  among  the 
most  noted  engineers.  The  Croton  dam  was  delayed  years  on 
account  of  such  conflicting  opinions.  As  this  book  goes  to  press 
the  professors  of  University  College,  of  London,  England,  come 
out  with  the  startling  announcement  that  all  previous  dams 
have  been  designed  without  taking  into  account  a  force  tending 
to  burst  the  dam  vertically.  Following  is  given  a  clipping  from 


FIG.  233. 

a  London  paper,  which  shows  how  the  best  laid  plans  go  oft 
agley.: 

"  The  new  theory  regarding  the  strain  upon  masonry  of 
dams,  brought  forward  by  Atcherley  and  Pearson,  mathema- 
ticians of  the  University  College  of  London,  has,  at  least  for  the 
time  being,  put  an  end  to  Sir  William  Garstin's  plan  of  raising 
the  gigantic  dam  at  Assouan,  which  has  already  proved  such  a 
blessing  to  Egypt. 

'  This  was  an  important  part  of  a  huge  plan  for  further  irriga- 
tion of  Egypt,  destined  to  bring  millions  of  acres  under  cultiva- 
tion. Lord  Cromer's  last  report  dealt  minutely  with  the  scheme, 
the  outlines  of  which  then  were  cabled. 

"  Sir  William,  through  calculations  of  the  engineering  staff, 
was  satisfied  that  according  to  all  accepted  theories  of  dam 


HYDRAULIC  CONSTRUCTION.  251 

construction  the  factor  of  safety  was  amply  sufficient  to  permit 
the  dam  being  raised,  but  in  October  he  was  informed  of  the  new 
theory  that  the  vertical  sections  of  dams  under  water  pressure 
were  more  severely  strained  than  the  horizontal  parts. 

'  Therefore,  while  the  dam  was  designed  according  to  rules 
hitherto  applied  and  may  be  safe  as  regards  cracking  horizontally, 
it  may  crack  vertically. 

'  The  Egyptian  Government  asked  Sir  Benjamin  Baker  to 
give  an  opinion  on  the  raising  of  the  dam.  After  inspecting  the 
dam  Baker  reported  that  all  thoughts  of  raising  it  should  be 
postponed  another  20  years. 

'  He  is  of  the  opinion,  basing  it  on  the  new  theory,  that  there 
now  is  little  hope  of  raising  the  dam  to  any  appreciable  extent, 
although  calculations  submitted  to  and  passed  by  him  before 
the  new  theory  was  correct  in  all  respects.  He  adds  that  the 
vibrations  on  the  masonry  dam  are  due  to  the  rushing  water  in  the 
sluices,  and  that  the  dam  as  constructed  is  perfectly  safe. 

"  'There  should  be  '  he  said, '  perfect  confidence  and  no  need 
of  anxiety  in  the  permanent  stability  for  centuries  without 
difficult  or  costly  works  for  its  maintenance.'  ' 

Masonry  Dam  Design  in  Detail. 

The  design  of  masonry  dams  will  now  be  treated  in  detail. 
First,  take  the  case  of  a  dam  (Fig.  234)  having  the  water  level 


FIG.  234. 
with  the  crest  and  the  up-stream  side  (face)  perpendicular.     The 

TV 

pressure  at  P  =  y  X62.5X//  and,  in  effect,  is  applied  at  the 

point  J  H  from  the  bottom.  The  pressure  P  acts  perpendicular 
to  the  face,  and  in  turning  the  dam  over,  uses  the  lever  A  B. 
That  is,  the  pressure  P  in  pounds  times  A  B  in  feet,  is  the  over- 
turning moment. 


252  HYDROELECTRIC  PLANTS. 

The  center  of  gravity  G  is  found  by  drawing  lines  from  C  to 
.the  middle  of  B  D,  and  taking  ^  of  it.  The  weight  of  the  masonry 
,  (due  allowance  being  made  for  the  flotation  factor)  may  now  be 
supposed  to  act  at  this  point,  and  in  holding  the  dam  against 
.the  overturning  force  of  the  water,  use  the  lever  BE,  EX  being 
drawn  through  the  center  of  gravity  and  perpendicular  to  D  B, 
therefore  the  resisting  moment  due  to  the  weight  of  the  dam 
js  WxBE  where  W  is  the  effective  weight  of  the  dam.  The 
factor  of  safety  of  the  dam  is 


PXAB 

In  all  these  examples  one  linear  foot  of  the  dam  is  considered, 
i.e.,  the  pressure  for  100  feet  of  dam  would  be  100P. 

Suppose  the  dam  to  be  turned  around,  as  in  Fig.  235.  The 
water  pressure  acts  perpendicular  to  the  face  and  at  a  point 


FIG.  235. 

P,  J  the  height  as  before.  P  acts  in  overturning  the  dam  with 
the  leverage  A  B,  which  is  the  perpendicular  distance  between 
the  projection  of  P  and  the  toe  of  the  dam  B.  It  will  be  seen 
that  the  flatter  the  face  C  D  the  greater  will  be  the  moment  of 
the  vertical  force.  That  is,  the  more  nearly  the  dam  approaches 
the  gravity  type  the  less  the  tendency  of  the  water  to  tip  it  over. 
The  center  of  gravity  is  found  as  before  and  the  perpenidcular, 
%  E,  is  drawn.  Then  the  effective  weight  of  the  dam  will  act, 
in  resisting  the  water  pressure,  through  the  leverage  E  B,  there- 
fore the  factor  of  safety  is 

WXEB 
PXBA 

Now  take  the  case  of  Fig.  236,  where  the  water  is  flowing  over 
the  dam  at  a  depth  h< 


HYDRAULIC  CONSTRUCTION. 


253 


In  this  case  P  is  not  applied  at  a  distance  of  J  H  from  the  base, 
but  at  a  distance 


V  =— 
3 


h_ 
+  X 


The  overturning  moment  of  the  water  then  =  PxA  B.  <  i 
To  get  the  center  of  gravity  of  a  section  like  this,  draw  a  line 
connecting  the  centers  of  the  lines  D  B  and  F  C.  Lay  off 
RF  equal  to  D  B,  and  D  S  equal  to  F  C.  Then  where  R.S 
crosses  the  center  line,  will  be  the  center  of  gravity.  The  resist- 
ing moment  of  the  dam  =  W  X  E  B  and  the  factor  of  safety  is 

WXEB 


s  = 


PXAB 


If  this  section  is  turned  as  in  Fig.  235  the  same  reasoni  i  g  is 
true. 


FIG.  236. 

A  common  method  of  determining  the  safety  of  any  section  is  to" 
lay  off  to  scale  from  /  (Fig.  236)  the  line  /  K  equal  to  the  pressure 
P,  and  from  7  the  line  7  N,  to  the  same  scale  representing  the 
effective  weight  of  the  dam.  In  gravity  type  the  weight  of  the 
water  should  be  considered.  Then  the  resultant,  7  M,  should 
intersect  the  base  B  D  in  the  middle  third.  Such  a  method  is 
faulty,  as  it  does  not  take  into  consideration  the  factors  2,  3,  4. 
6,  7  or  8  (page  239),  but  will  serve  for  the  basis  of  further  design. 
After  getting  this  preliminary  section  the  forces  due  to  vacuums, 
ice  expansion,  character  of  bottom,  etc.,  can  be  considered  and 
extra  area  of  section  added. 

As  shown  by  Fig.  235  the  dam  is  safest  against  the  water 


254 


HYDROELECTRIC  PLANTS. 


pressure  with  the  slope  up  stream.  Especially  is  the  factor  of 
safety  against  sliding  increased,  but  there  is  the  overpour  to  be 
considered.  In  order  to  conduct  the  water  away  from  the  dam 
in  safety,  an  apron  is  required,  and  if,  in  addition  to  the  apron, 
the  dam  is  sloped  up  stream  the  result  is  a  dam  too  expensive 
to  build.  For  this  reason  practically  all  masonry  dams  are  built 
with  the  face  about  perpendicular,  the  slight  up-stream  slope 
given  to  some  being  merely  a  temporizing  between  cost  and 
safety. 

Therefore  to  design  a  masonry  dam,  first  design  the  apron, 
giving  the  necessary  slope  to  prevent  vacuum  (Fig.  237),  and 
then  lay  off  the  section  c  f  d  6,  as  found  for  Fig.  236,  having 
the  resultant  of  the  water  pressure  and  gravity  of  the  dam  strike 


FIG.  237. 


in  the  middle  third  of  the  base.  Now  add  the  section  /  r  t  d 
of  area  sufficient  to  make  the  dam  safe  against  ice  expansion, 
seepage,  shearing  and  the  weakness  of  green  masonry.  The 
flotation  will  have  been  allowed  for  in  determining  W,  and 
undermining  will  have  been  provided  for  in  building  a  liberal 
apron.  Such  a  masonry  dam  should  be  safe,  providing  foun- 
dations are  good,  and  the  materials  are  well  laid.  After  the  sec- 
tion has  been  decided  upon  it  is  well  to  investigate  the  critical 
points  to  see  if  the  safe  crushing  strength  has  not  been  ex- 
ceeded. 

In  General  Gillmore's  reports  we  find  the  following  table  of 
the  crushing  strength  in  tons  per  square  foot  (2240  pounds)  for 
various  stones: 


H  YDRA  ULIC  CONSTR  UCTION. 


255 


99  specimens  of  granite. 
43  "  limestone. 

12          "  "  marble. 

62          "  "  sandstone. 


Highest  1541  tons. 
1600     " 
1284     " 
1136     " 


Lowest  497  tons. 
"       221     " 
488     " 
"       251     " 


The  lowest  values  are  from  the  poorest  quarries  in  the  United 
states,  so  it  would  seem  that  by  taking  one-tenth  of  the  minimum 
values  one  would  have  reached  the  extreme  of  safety.  However, 
in  the  design  of  the  Quaker  Bridge  dam  (Croton  dam)  for  the 
New  York  City  water  supply,  the  engineers  limited  the  safe 
crushing  strength  to  13.5  tons  or  30,000  pounds  per  square  foot. 

Crushing  stresses  are  determined  as  follows: 

In  Fig.  238,  let  L  equal  the  base  of  the  dam,  d  the  distance 


FIG.  238. 

between  a  point  where  a  perpendicular  passing  through  the 
center  of  gravity  cuts  the  base  and  the  up-stream  edge  of  the 
dam.  Then  L  —  d  is  the  distance  from  B  to  D.  Let  p  be  the 
maximum  unit  stress  then 


and 


P  = 


P' 


W  (L-d) 
Ld 


Ld 


wherein  W  is  the  effective  weight  of  the  dam. 

The  resultant  MI  is  found  as  in  Fig.  238.  By  measure- 
ment on  the  drawing  the  distance  d  is  found,  and  substi- 
tuting in  the  above,  p  for  the  segment  d  may  be  deter- 
mined, this  gives  the  maximum  compressive  stress  in  the  base 
at  that  point  in  pounds  per  square  foot,  when  the  pond  is  empty. 
To  find  the  stress  near  B  due  to  the  water  pressure  measure  d' 
and  substitute  in  the  above  formula.  The  answer  will  be  the 
pressure  near  B  in  pounds  per  square  foot. 


256 


HYDROELECTRIC  PLANTS. 


In  designing  a  very  high  dam  the  first  operation  is  similar 
to  the  preceding:  the  top  section  assuming  H  =  100  feet  (Fig. 
239)  is  taken  first.  Find  the  point  of  application  of  the  water 
pressure  P,  as  in  Fig.  236.  Find  the  center  of  gravity  g  and  g' 
of  each  of  the  triangles  ABC  and  A  E  D  as  already  explained. 
Find  the  center  of  gravity  of  these  two  triangles  as  follows: 

/       W    \ 
distance  g  G  =  g  g'  (w+w,) 

wherein  W  and  W  are  the  weights  or  areas  of  the  triangles 
whose  centers  of  gravity  are  respectively  g  and  g'. 

A'e 


distance 


(4 '       \  •  •  I 

— j-y-  I  where  Ag  and  A ' g  are  the  areas  of 
Ag  +  A  g/ 


FIG.  239. 


the  triangles,  of  which  they  are  the  center  of  gravity.  The  triangle 
ABC  is  added  on  to  give  a  strong  crest.  The  base  E  D  is 
arbitrarily  taken  as  two-thirds  the  height  //.  The  resultant 


/  M    is  next  obtained,  and  from  p  =  W 


(L  -  d] 
Ld 


the  maximum 


pressures  are  found.  Second,  if  the  pressures  of  the  first  section 
are  within  the  limits  of  safety  another  section  of  50  feet  is  added 
(Fig.  240),  the  tip-stream  face  being  given  a  batter  of  15  feet 
in  the  50,  and  the  apron  a  batter  of  40  feet  in  the  50.  (These 
proportions  conform  to  the  standard  sections  for  such  dams, 
(see  Fig.  241.) 

The  center  of  gravity  of  the  entire  figure  A  B  C  D  H  F  E  is 
now  found.     The  center  of  gravity  of  E  D  H  F  being  found  as 


HYDRAULIC  CONSTRUCTION. 


257 


in  Fig.  236,  and  then  that  of  the  two  centers  of  gravity  G  and  g", 
found  from 


wherein  w  and  w"  are  the  weight  or  areas  of  the  sections  whose 
centers  of  gravity  are  G  and  g"  respectively.  Gf  is  the  center 
of  gravity  of  the  entire  section. 

Find  P  for  the  dam  now  150  feet  high  and  its  point  of  appli- 
cation in  the  same  way  as  for  the  100-foot  section. 

As  the  face  of  the  dam  has  now  been  given  a  batter  of  15  feet 


FIG.  240. 

up  stream,  there  will  be  a  certain  component  of  force,  due  to 
the  water  holding  the  dam  down.  This  will  be 

50 
(100  + 10 +-^-)  X  62. 5X15  =  126,562. 5  pounds.      Thiswillact 

perpendicular  to  the  base  F  H  and  at  a  point  half  way  between 
E  and  F.  This  large  component  is  not  generally  considered  in 
the  design  of  the  dam,  and  while  its  neglect  is  on  the  side  of 
safety,  in  finding  the  pressure  on  the  toe  H,  it  adds  to  the  pres- 
sure on  the  base  at  F,  and  the  author  believes  that  if  there  is 
any  reliability  at  all  in  the  designing  of  a  dam,  every  factor 
should  be  allowed  for.  Therefore,  to  allow  for  this  force  con- 


258 


HYDROELECTRIC  PLANTS 


sider  the  126,562.5  pounds  as  being  so  much  area  or  weight  of 
masonry  concentrated  at  O,  after  having  divided  it  by  the  weight 
of  a  cubic  foot  of  the  dam  materials  to  reduce  it  to  the  same 
standard  with  the  former  calculations.  Thus,  if  the  masonry 
weighs  140  pounds  the  equivalent  at  O  =  904.02  square  feet. 

Now  connect  O  and  G'  and  find  the  center  of  gravity  of  these 
two  areas,  and  from  the  point  so  found,  drop  a  perpendicular  to 
the  base  F  H  and  on  this  new  component  lay  off  to  scale  the 


FIG.  241. 

amount  of  the  combined  forces  due  to  G'  and  0  and  draw  the 
resultant  S  Mf. 

The  effect  has  been  to  throw  the  resultant  more  toward  the 
center  of  the  base,  which  is  as  it  should  be.  The  pressure  of  the 
dam  when  the  pond  is  empty  may  be  too  great  at  F  and  possibly 
exceed  the  stress  allowed,  therefore  the  slope  E  F  may  have  to 

be  increased.     From  p  = j—^ the   pressure  at   F  can  be 

calculated  for  either  d  or  d"  and  at  H  for  either  df  or  d'" . 

If  the  pressures  are   satisfactory   lay   down   another  50-foot 


HYDRAULIC  CONSTRUCTION.  259 

section  and  proceed  as  before.  Each  of  the  succeeding  sections 
batter  50  feet  down  stream,  up  stream  the  third  section  batters 
20  feet,  the  fourth  30  feet,  the  fifth  50  feet,  etc.  Of  course  these 
batters  are  arbitrary  and  are  only  to  serve  as  a  preliminary 
guide. 

EXAMPLE.  —  As  example,  assume  a  dam  250  feet  high,  with  10 
feet  of  water  going  over  its  crest  ;  also  assume  the  masonry 
weighs  130  pounds  per  cubic  foot,  allowing  10  pounds  for  flota- 
tion, and  that  the  safe  bearing  strength  is  20,000  for  d  and 
15,000  for  d'.  Now  assume  the  section  to  be  the  same  as  the 
standard  dam  (shown  in  Fig.  241  by  the  dotted  outline).  Then 
the  crest  is  20  feet  wide  and  formed  of  a  triangle  20  feet  wide 
at  base  and  30  feet  high  superimposed  on  the  triangle  100  feet 
high  and  with  a  base  two-thirds  the  height  or  66|  feet.  The 
calculations  for  this  first  section  follow: 

First  section.  The  center  of  gravity  for  each  triangle  is  found 
and  the  center  of  gravity  G  of  the  two  areas  determined  as 
explained  above.  Then  calculate  the  water  pressure  against 

(TT  \ 

-j  +  h),   which    for    this    section  is, 

P  =  62.5  X  100  (         +  lo    =  375,000. 


The  point  at  which  P  is  applied  is  the  distance  Y  above  the 
base  thus, 


-R  A  ,   Jt_\ 

"   3    V         JT+21J 


which  here  is 


100 
3 


The  force  P  is  projected  horizontally  as  shown  by  the  arrow 
heads.  A  perpendicular  line  is  dropped  from  the  center  of 
gravity  G,  and  projected  till  it  intersects  P.  From  this  inter- 
section measure,  to  any  convenient  scale,  the  force  P,  horizon- 
tally, and  the  weight  of  the  section,  W,  downward,  as  shown, 
complete  the  rectangle  and  draw  the  resultant.  Now  measure 
the  distance  from  the  intersection  of  this  resultant  with  the 
base  of  the  dam  to  the  right  hand  edge  of  dam,  this  is  d'  and 


260  HYDROELECTRIC  PLANTS. 

in  this  case  equals  14.5'.  Also  measure  the  distance  from  the 
perpendicular  from  the  center  of  gravity  to  the  up-stream  edge 
of  the  dam,  d  =  21.5  feet.  Areas  about  G  =  300  +  3333.5  = 
3633.5.  W  =  (300  +  3333.5)  130  =  472,355  pounds. 

W(L-d) 

Maximum  pressure  pmax  =  —  ~—  7  — 

L/  d 

and  for  d, 

472355  (67-  21.5) 


max  g^vxoi    g 

O/  X  ^1  •  O 

for  d', 

472355  (67-  14.5)' 
pmax  =  -  A7     1  A    -       - 
o/  X  14  .  o 


=  14,989  pounds  per  square  foot. 


25,525  pounds  per  square  foot. 


This  gives  a  pressure  on  the  up-stream  side  of  dam  below  the 
assumed  allowable  stress  of  20,000,  but  the  pressure  on  the  down- 
stream side  is  much  too  high,  therefore  the  section  is  altered 
giving  the  base  a  width  of  80  feet. 

Then  the  area  about  G  is  240  +  4,000  =  4240. 

W  =  4240X130  =  551,200  pound*. 

551,200  (80-  26) 
Pmax  at  d  --=  -  8QX26  =  14,310  pounds  per  square  ft. 

551,200  (80-  30) 
pmax  ^  d'  =  -  80X30  -    =  n'525P°undsPers(luareft- 

We  now  have  the  pmax  at  dr  somewhat  lower  than  the  lim- 
iting value  but  this  is  necessary  to  keep  the  slope  further  down 
from  becoming  too  flat. 

In  all  these  calculations  it  is  assumed  that  the  extreme  edge 
of  the  down-stream  toe  would  not  crumble  if  the  dam  should 
turn  on  it  as  a  pivot.  This  would  not  be  true  as  it  would  break 
back  to  some  point,  A  and  therefore  d'  should  only  be  figured 
to  that  point.  This  would  greatly  increase  the  pmjx*  How- 
ever, the  authorities  do  not  generally  allow  for  it. 

Neither  has  the  vertical  component  of  the  water  pressure 
which  would  greatly  increase  the  pmax  at  the  up-stream  edge 
of  the  dam  been  allowed  for  here. 


HYDRAULIC  CONSTRUCTION.  261 

Second  section.    Now  add  50  feet  more  of  dam  as  shown  and, 


62.5X150  +10     =  796,875  pounds. 


Areas  about  G'  =  240  +  4000  +  5625  =  9865  square  feet. 
W  =  9860X130  =  1,282,450  pounds. 

Completing  the  parallelograms  of  forces, 
for  d, 

1,282,450  (145-53) 
Anax  =  ~         145  v^r"          =  pounds  per  square  foot. 


ford', 

1,282,450  (145-59) 
-  --  145x59  - 


13120  pounds  per  square  foot. 


These  values  being  sufficiently  safe,  another  50  feet  of  dam  is 
added. 

200 
Third  section.   P  =  62.5X=^  (200  +  10)  =  1,375,000  pounds. 

200   /,  10 


Areas  about  G"  =  240  +  4000  +  5625  +  9250  =  19,115  square 
feet. 

W  =  19,115X130  -  2,484,950  pounds. 

Completing  the  parallelogram, 
ford, 

2,484,950  (225-87) 
£max  =  -         225X87 =   1751°  P°unds   Per    square  foot. 

and  for  d', 

2,484,950  (225-99) 
/>max=    -     — 225x99""         =  pounds  per  square  foot. 

Each  of  these  pressure  seems  to  be  approaching  our  assumed 
limits  so  another  50  foot  section  is  added. 


262  HYDROELECTRIC  PLANTS. 

Fourth  section.      P  =  62.5X250  (250/2  +  10)  =  2,109,375. 
250   /  10 


)• 


Areas  about  G"f  =240  +  4000  +  5625  +  9250+13,750 
32865  square  feet. 

W  =  32865X130  =  4,272,450 
Completing  the  parallelogram  of  forces, 
ford, 

4,272,450(324-138.5) 


324X138.5 
and  for  d', 

4,272,450  (324  -  143) 


17.661  pounds  per  square  foot. 
=  13, 187  pounds  per  square  foot. 


max 324X143 

The  values  assumed  above  for  the  compressive  strength  of 
the  masonry  are  very  low,  but  will  serve  to  illustrate  the  method. 
If  the  drawing  is  made  to  a  scale  of  J-inch  to  the  foot,  and 
carefully  done,  the  degree  of  accuracy  will  be  well  within  all 
requirements. 

The  crest  would,  of  course,  have  to  be  given  a  different  shape 
as  explained  on  page  254  for  an  overflow  dam. 

The  outline  of  a  standard  dam  section  is  shown  in  Fig.  241. 
This  is  for  a  dam  which  allows  for  no  overflow  and  which  as- 
sumes a  cubic  foot  of  masonry  at  140  pounds.  The  assumption 
of  weight  is  very  important  and  the  writer  thinks,  that  owing 
to  the  difference  in  opinion  on  the  subject,  this  is  much  too  high. 
Again  the  crushing  strength  on  the  up-stream  side  is  limited 
by  the  strength  of  the  mortar,  and  not  the  stone.  Also,  in 
'finding  the  value  for  pmax  on  the  up-stream  side,  the  maximum 
weight  of  the  masonry  must  be  used  because  it  is  when  the 
reservoir  is  empty,  and  there  is  no  flotation,  that  this  stress 
will  reach  a  maximum.  This  involves  the  construction  of  a 
second  parallelogram  for  each  section,  having  W  figured  with  the 
weight  of  masonry  at  170  to  180  pounds  per  cubic  foot. 

Again,  suppose  the  back  water  stands  at  the  level  of  the 
top  of  last  section,  then  the  weight  of  this  section  must  be  figured 
as  having  lost  62.5  pounds  per  cubic  foot  of  masonry  at  all 
times.  Being  buried  in  the  earth  does  not  alter  the  calcula- 
tions, all  of  which  are  figured  from  solid  rock  bottom. 


HYDRAULIC  CONSTRUCTION.  263 

The  height  of  such  a  dam  is  only  limited  by  the  compressive 
strength  of  the  masonry  (the  tensile  strength  is  not  considered) 
and  the  cost.  The  Croton,  or  Quaker  Bridge  dam  is  300  feet 
high  at  the  highest  point. 

Examining  the  four  sections  of  the  preceding  examples  for 
this  factor  of  safety  we  find: 

44  X  551  200 
First  section  factor  of  safety  =  36>  Ix375>oou  =  1-78. 


c  t  t      t  +  82X1,282,450 

Second  section  factor  of  safety  =   -=: — __-  0_.  •  =  2.48. 


Third  section  factor  of  safety  -  =  3.21. 


In  the  above  we  have  taken  44.82  and  124  as  the  leverage  to  the 
probable  breaking  line  of  toe.  As  the  factors  are  increasing, 
we  need  not  begin  the  fourth  section. 

The  above  factors  do  not  allow  for  the  tensional  strength, 
which  is  the  only  safe  way  to  figure,  and  it  therefore  would 
seem  that  the  first  section  is  weak.  In  no  other  branch  of 
engineering  would  such  a  small  factor  of  safety  be  used.  On 
the  first  section  there  is  no  vertical  component  of  water  pres- 
sure to  add  to  the  factor  of  safety,  the  safety  of  this  is  out  of 
all  proportion  to  the  other  sections. 

In  the  second  section  if  the  vertical  component  of  the  water 
pressure  is  to  be  allowed  for,  proceed  as  follows:  Vertical  pressure 
P  =  135X62.5X15  =  126,562.5  pounds.  This  acts  at  a  point 
midway  between  B  and  C  and,  in  effect,  acts  the  same  as  so 
much  masonry,  whose  center  of  gravity  is  at  that  point;  there- 
fore connect  this  point  by  a  horizontal  line  with  the  perpen- 
dicular Gf  T,  and  get  the  center  of  gravity  of  126,562.5  pounds 
at  R,  and  1,282,450  pounds  at  S,  as  follows: 

By  measurement,  RS  =  46  feet. 

R  U  -  46  1'282'450 


1,282,450  +  126,562 
and 

.911X46  -  41.9  feet. 


264  HYDROELECTRIC  PLANTS. 

W  now  =  1,282,450+126,562  =  1,409,012  pounds  and  acts 
through  U.  Lay  off  from  U  the  vertical  U  F  to  same  scale  as 
W  and  construct  the  parallelogram  of  forces,  P  remaining  the 
same.  The  resultant  now  strikes  the  base  at  Z  and  the  factor 

of  sa         is  now,    '        I     '  '     ^  =  2.87  instead  of  2.48  as  before. 
oox  /yo,o«  o 

The  pmax  for  d  is  also  increased  for  the  second  section. 


7Q     5\ 

=    1,409,012      145X49'5     =  !8,750  pounds  per  square 

foot  instead  of  15,350  as  before. 

The  /?max  is,    of  course,    decreased  on  d'  but  this  is    of    no 
importance. 

There   are   several  methods  of   solving  the   above   problem, 


FIG.  242. 

but  the  center  of  gravity  method  is  the  one  most  readily  under- 
stood by  the  average  engineer. 

Such  dams  are  now  frequently  made  of  concrete,  and  when 
properly  made  are  superior  to  masonry.  Large  quantities  of 
concrete  hastily  built  are  dangerous  in  any  structure,  but  es- 
pecially so  for  dams.  Severe  stresses  are  set  up  by  the  shrink- 
age of  the  mass  on  setting.  The  outside  contracts  first  and 
later  the  interior,  causing  intense  strains*  which  result  in  cracks 
or  cause  the  dam  to  give  way  under  small  added  pressures. 

Therefore,  the  concrete  should  be  deposited  in  blocks  as  in 
Fig.  242.  The  blocks  A,  C  and  B  are  built  in  place  by  suitable 
forms  and  after  they  have  set  for  two  or  three  weeks,  the  blocks 
E,  D  and  F  are  laid.  A,  B  and  C  are  lower  by  a  foot  or  so 
than  the  others,  so  as  to  afford  the  proper  friction  between  the 
layers.  The  blocks  may  be  attached  to  each  other  by  means 
of  steel  anchors  as  shown  in  the  block  D. 


HYDRAULIC  CONSTRUCTION.  265 

Steel  bars  placed  as  shown  by  dots  on  Fig.  242  will  make 
the  factor  of  safety  what  it  should  be;  this  reinforcing  will  be 
especially'  advisable  in  the  case  of  high  dams  where  the  factor 
against  overturning  is  small  near  the  crest. 

Edward  Wigman,  a  noted  authority  on  masonry  dam  con- 
struction, states  the  following  in  his  admirable  book:  "  As  the 
theory  of  masonry  dams  has  to  be  based  upon  hypotheses 
which  are  only  approximately  correct,  we  may  permit,"  etc. 

He  also  gives  the  following  for  the  safety  of  a  masonry  dam 
against  sliding:  /  W  =  horizontal  thrust,  P,  of  the  water.  W  = 
weight  of  dam,  and  /  =  coefficient  of  friction  of  masonry  on 
masonry  usually  figured  as  .67  to  .75. 

EARTH   DAMS. 

The  earth  dam  is,  without  doubt,  the  oldest  form  of  dam, 
yet  in  this  country  it  has  been  looked  upon  with  a  good  deal 
of  suspicion.  Hundreds  of  the  largest  cities  in  the  country 
are  to-day  depending  on  earth  dams  to  hold  the  water  which 
is  to  save  their  millions  from  thirst  and  fire.  For  all  this  when 
the  engineer  is  asked  to  consider  the  building  of  an  earth  dam 
for  a  water  power,  there  is  at  once  a  vigorous  protest. 

There  are  several  very  good  reasons  why  an  earth  dam  may 
be  superior  to  the  solid  concrete  or  masonry  dam,  given  that 
it  be  properly  constructed.  No  sudden  crack  can  destroy  the 
whole  structure.  Any  trouble  which  may  develop  will  or- 
dinarily give  warning  in  time  to  permit  of  repairs.  The  Johns- 
town flood  is  pointed  to  as  an  example  of  the  insecurity  of  such 
dams.  However  the  cause  of  this  disaster  was  due  to  insuffi- 
cient spillways  and  no  one  claims  that  an  earth  dam  is  built 
for  spillway  purposes. 

A  large  majority  of  the  failures  of  earth  dams  have  been  due 
to  this  cause.  The  second  in  order  of  the  causes  of  failure  is 
the  placing  of  pipes  through  the  embankment.  Build  the 
dam  so  that  the  spillway  is  ample  and  in  the  proper  place, 
place  no  pipes  through  the  fill  and  use  the  proper  materials 
and  the  earth  dam  is,  without  question,  the  best  and 
cheapest  dam  that  can  be  built. 

Mr.  Burr  Bassell  in  his  book,  "  The  Earth  Dam,"  treats  the 
subject  at  length. 

There  have  been  built  eleven  dams  over  100  feet  high,  ten 


266  HYDROELECTRIC  PLANTS. 

over  90  feet  high,  and  six  over  80  feet  high.  In  Europe  the 
earth  dam  has  received  considerable  study  and  many  dams  are 
standing  which  are  exceedingly  old. 

That  an  earth  dam  should  be  suited  to  a  site  there  must  be 
present  three  conditions.  First,  the  conditions  must  be  such 
that  the  maximum  flood  which  has  ever  occurred  at  the  place 
can  be  taken  care  of  without  washing  out  the  uncompleted 
structure.  Second,  the  conditions  must  be  such  that  the 
maximum  floods  which  are  to  be  expected"  can  be  diverted 
around  one  end  of  the  dam,  over  the  rim  of  the  containing  cliffs 
or  through  some  new  channel  so  that  at  no  time  in  the  future 
can  the  waters  top  the  embankment.  Third,  the  materials 
must  be  suited  to  the  work. 

Mr.  Burr  Bassell  advises  that  where  a  tunnel  of  sufficient 
size  to  carry  all  the  flood  water  can  not  be  cut  around  the  dam 
through  solid  rock,  or  where  the  channel  can  not  be  entirely 


FIG.  243. 

changed  to  bring  about  the  same  degree  of  safety  during  con- 
struction, that  the  earth  dam  should  not  be  built!  This  is 
certainly  worthy  advice  from  the  strongest  advocate  of  an 
earth  dam,  but  it  should  be  possible  to  use  the  idea  shown  in 
sketch,  Fig.  243. 

The  author  was  called  upon  to  pass  on  the  leasibility  of  an 
earth  dam  near  Baltimore  where  it  was  impossible  to  take 
care  of  the  water  in  any  other  way  than  in  the  one  shown  in 
the  sketch.  The  arches  of  the  concrete  bridge  could  be  made 
of  great  span  so  as  to  take  care  of  the  greatest  floods  during 
construction.  When  the  earth  fills  were  completed  a  dry  period 
would  be  selected  and  the  water  made  to  run  through  a  com- 
paratively small  pipe  until  all  the  space  under  the  arches  was 
filled  with  concrete.  Then  the  small  pipe  could  be  closed  also 
or  left  with  a  gate  for  future  use. 

The  best  form  of  spillway  is  where  the  dam  is  of  such  height 


HYDRAULIC  CONSTRUCTION. 


267 


that  by  slight  excavation  the  water  may  be  made  to  spill  over 
the  rim  of  the  basin  above  the  dam.  The  capacity  of  this 
spillway  may  be  determined  by  computing  the  maximum  flow 
as  explained  in  Chapter  III.  Where  the  flood  flow  is  small  the 
tunnel  may  be  resorted  to. 

There  are  certain  materials  which  are  of  no  use  for  building 
earth  dams.  It  is  the  author's  opinion  that  all  these  dangerous 
materials  contain  what  is  commonly  called  quicksand. 

The  test  for  such  earths  is  to  mix  the  material  up  fairly  wet 
in  a  box  and  pack  it  with  a  tamp.  If  it  quakes  on  being 
tamped  it  belongs  to  the  dangerous  class.  Good  earth  should 
pack  solidly  into  place. 

Another  test  is  to  find  at  what  angle  the  earth  will  stand 
when  piled  up  in  water.  This  angle  should  not  be  less  than  20 
degrees.  The  best  soils  for  the  purpose  contain  some  clay. 


fli'-t 


FIG.  244. 


Puddle  is  a  term  given  to  that  part  of  the  fill  which  is  made 
of  selected  materials  mixed  together  to  form  a  core  to  prevent 
seepage.  Many  engineers  contend  that  the  best  earth  dam  is  one 
of  homogeneous  section.  Mr.  Bassell  placed  the  core  of  the 
Tabaud  dam  on  the  up-stream  edge  (see  Fig.  244),  and  this  is 
undoubtedly  the  proper  place  for  it  if  it  is  used  at  all.  Mr. 
Herbert  M.  Wilson  advises  the  following  mixture  for  puddle: 

Coarse  gravel 1.0  cubic  yard 

Fine  gravel 35 

Sand... 15  "   -      " 

Clay 20  ' 

1.70  " 

which,  when  rolled  in  embankment,  gives  1J  yards. 

All  clay  shrinks  on  drying,  and  if  allowed  to  dry  out  while 
being  compacted  the  result  will  be  a  leaky  and  dangerous  dam. 


268  HYDROELECTRIC  PLANTS. 

Pure  clay  shrinks  about  five  per  cent,  on  drying.  Dry  clay 
as  usually  excavated  will  absorb  one-sixth  its  weight  of  water 
and  when  perfectly  dry  about  one-third.  Some  clayey  mix- 
tures while  hard  to  excavate  will  run  like  oil  when  wet. 
The  cost  of  well-made  puddle  varies  between  wide  limits, 
but  should  not  cost  more  than  from  20  to  40  cents  per  cubic  yard. 

The  safest  way  to  test  materials  for  imperviousness  is  to 
fill  the  ends  of  glass  tubes  all  to  the  same  depth  with  the 
materials  and  fill  the  tubes  with  water.  The  tube  which 
holds  the  water  the  longest  is  the  most  impervious.  Mr. 
Bassell  advises  building  the  dam  up  in  layers  which  have 
a  slope  toward  the  center  as  shown  in  Fig.  245.  This  is 
to  prevent  the  water  used  in  compacting  from  going  to  waste 
over  the  sides  of  the  embankment  and  to  insure  the  con- 
tinued dampness  of  the  layers  exposed  to  the  air.  The  thinner 
the  layers  the  more  thoroughly  can  they  be  compacted.  Six 
inch  layers  were  used  near  the  bottom  of  the  Tabaud  dam  and 
nine  inch  at  the  top. 


FIG.  245. 

The  process  then  s  as  follows:  The  earth  is  brought  to  the 
dam  in  wagons  or  by  aerial  cable  and  deposited  in  regular  heaps 
over  the  proper  area.  Road  graders  drawn  by  six  horses 
then  spread  out  the  piles  and  a  sprinkling  cart  drawn  by  four 
horses  wets  it  down.  A  five  to  eight  ton  roller  passes  to  and 
fro  over  the  wet  earth  and  finally  before  the  next  layer  is  de- 
posited, a  harrow  roughens  up  the  surface.  Every  surface  is 
kept  wet  at  all  times.  While  all  the  most  impervious  materials 
should  be  deposited  on  the  up-stream  side,  no  great  expense 
should  be  incurred  in  doing  so  as  it  will  be  better  to  spend  that 
extra  amount  in  making  the  dam  wider  at  the  base. 

Where  the  fill  is  made  by  hydraulicing  it  is  impossible  to  sort 
out  the  materials,  but  in  that  case  it  is  not  necessary. 

Common  practice  seems  to  make  the  top  width  about 
25  feet,  the  up-stream  slope  1:3,  and  the  down-stream  slope  1:2. 


HYDRAULIC  CONSTRUCTION.  269 

There  can  be  no  hard  and  fast  rule,  however,  as  the  slopes 
depend  on  the  angle  of  repose  of  the  materials,  and  the  width 
at  the  top  is  merely  the  factor  of  safety  for  the  particular  con- 
dition. 

Fig.  246  shows  a  section  of  the  Jerome  Park  Reservoir  for 
the  City  of  New  York.  Here  the  masonry  core  rests  on  quick- 
sand. It  would  seem  that  in  the  light  of  the  recent  development 
of  steel  sheet  piling,  that  piling  driven  to  bed  rock  would  be  a 
much  better  arrangement. 

The  greatest  chance  for  seepage  is  along  the  original  surface 
which  the  dam  rests  on,  and  every  precaution  must  be  taken 
to  break  the  continuity.  Plowing  and  harrowing  should  be 
thoroughly  done  and  all  soft  mud  pockets  cleaned  out.  If  the 
bottom  is  earth,  a  row  of  steel  sheet  piling  should  be  driven. 


FIG.  246. 

The  force  required  to  take  care  of  and  compact  2000  cubic 
yards  per  day  of  materials  delivered  on  the  dam  will  be  about 
as  follows: 

Three  rollers,  one  ten-ton  and  two  five-ton,  drawn  by  six  horses. 

Two  graders,  drawn  by  six  horses. 

Three  water  tanks,  drawn  by  four  horses. 

Two  harrows,  drawn  by  two  horses. 

Three  carts,  drawn  by  one  horse. 

One  plow,  drawn  by  two  horses. 

The  total  cost  of  this  equipment  would  be,  exclusive  of 
horses,  about  $2500  and  the  cost  per  cubic  yard  of  the  com- 
pacted materials,  exclusive  of  the  equipment,  about  four  cents 
per  cubic  yard. 

The  question  of  drainage  is  one  of  great  importance.  There 
is  sure  to  be  more  or  less  spring  water  at  the  site  and  this  must 
all  be  provided  with  some  means  of  exit  without  letting  it 
wash  out  the  earth  composing  the  dam.  If  the  bottom  is  of 
rock,  trenches  as  in  Fig.  247  should  be  excavated. 


270 


HYDROELECTRIC  PLANTS. 


In  the  bottom  of  the  trenches  tile  covered  with  concrete  are 
placed.  The  trench  thus  made  serves  a  double  purpose  as  it 
not  only  takes  care  of  the  spring  water  but  also  acts  as  a  pre- 
ventative  to  seepage  along  the  natural  surface.  Where  the 
bottom  is  earth  the  spring  water  must  be  conducted  away  with 
great  care. 


FIG.  248. 


Each  spring  must  be  thoroughly  boxed  over  with  reinforced 
concrete  and  a  drain  built  as  in  Fig.  248  to  conduct  the  water 
away.  This  drain  should  not  run  at  right  angles  to  the  axis 
of  the  dam,  as  it  would  then  tend  to  produce  a  leak  through 
the  dam,  but  it  should  have  a  small  angle  with  the  axis,  making 


' 


FIG.  249. — Earth  dam. 


as  long  a  drain  as  possible  before  it  reaches  the  down  stream 
edgewof  the  dam. 

In  Figs.  249  and  250  are  shown  sections  of  the  Belle  Fourche 
dam  now  under  contract  in  South  Dakota,  the  contract  price 
for  this  dam  containing  1,600,000  cubic  yards  of  gumbo  was 
at  the  rate  of  61  cents  per  cubic  yard  (government  contract), 
but  this  included  spillways.  The  author's  experience  with 


HYDRAULIC  CONSTRUCTION. 


271 


»umbo  has  been  very  disastrous  and  it  would  be  considered  a 
dangerous  material  for  earth  dams  unless  the  slopes  were  at 
least  3:1  and  the  top  50  feet  wide. 


Figs.  251  to  252  illustrate  the  weir  which  is  to  be  built  intc 
the  top  of  the  earth  dam.     This  is  always  a  dangerous  thing  to  do. 


272 


HYDROELECTRIC  PLANTS. 


Longitudinal  Section 


1 J    _ 

Center  Line* 
Half         Plan 


Plan  . 


Section     A-B. 
FIGS.  251-252. 


//  YDRA  ULIC  CONSTR  UCTION. 


273 


Fig.  250  shows  how   the   concrete  pipe  is  laid  through  the  dam 
which  is  also  bad  engineering. 

Hydraulic  Fills. 

To  placer  mining  in  the  West  we  owe  the  cheapest  and  best 
method  for  making  a  fill  where  the  local  conditions  are  favorable. 

Where  a  giant  is  used,  water  must  be  delivered  to  it  at  a  head 
of  100  to  150  feet.  In  exceptional  cases  this  water  is  found 
within  reasonable  distance  to  the  materials  and  at  a  sufficient 
elevation  to  produce  the  necessary  head.  However,  in  the 
great  majority  of  cases  the  water  must  be  pumped  from  the 
river  to  be  dammed.  To  pump  the  water  a  centrifugal  pump 
may  be  used. 

In  such  cases  the  power  required  for  pumping  is  a  serious 


FIG.  253. — The  cross  sections  of  several  of  the  world's  most  famous 
earth  dams. 


item  and  wherever  possible  the  water  used  should  be  collected 
at  the  level  of  the  giant  and  used  over  and  over  again.  Thus 
a  pump  of  comparatively  small  size  would  pump  the  water 
from  the  river  up  to  the  giant  and  a  large  pump  at  the  giant 
would  pump  the  pressure  necessary  for  it. 

Fig.  254  shows  the  method  of  using  the  giant.  The  grade  of 
seven  to  ten  per  cent,  from  the  cliff  to  the  sluice  is  maintained,  at 
all  times.  The  sluice  may  be  a  metal  lined  box  or  may  be  simply 
a  ditch  dug  in  the  earth.  If  a  metal  lined  box  it  must  have  a 
slope  of  from  six  to  ten  per  cent.,  and  if  a  ditch,  25  per  cent.  The 
sluices  lead  the  earth  and  water  down  to  the  dam  where  the 


274  HYDROELECTRIC  PLANTS, 

semi-liquid  is  collected  in  a  lake  on  top  of  the  fill.  At  some 
suitable  location  a  timber  spillway  is  provided  so  that  the 
surface  water  is  drawn  off  without  any  of  the  earth  going  with 
it. 

The  amount  of  water  used  depends  largely  on  the  head  at 
the  giant  and  the  materials,  but  roughly  it  may  be  taken  at 
from  900  to  1500  cubic  feet  of  water  per  cubic  yard  of  materials 
in  the  dam. 

If,  as  was  the  case  with  the  La  Mesa  dam  in  California,  there 
is  no  embankment  upon  which  to  work  a  giant,  then  a  large 
area  of  soil  is  plowed  and  scraped  into  the  sluices.  At  the  La 
Mesa  dam  11  acres  were  excavated  to  a  depth  of  two  feet.  In 
this  way  700  cubic  yards  per  day  were  delivered  to  the  dam 
with  a  use  of  50,000  cubic  feet  of  water. 


FIG.  254. — Giant  washing  earth  into  sluice. 

About  the  largest  daily  average  fill  was  made  on  a  long 
railway  fill  where  for  60  days  the  average  was  1100  cubicjyards 
per  day. 

In  this  case  the  head  at  the  giant  was  160  feet  and  the  water 
used  was  960  cubic  feet  per  minute,  the  sluices  were  4x2  feet. 
The  costs  per  yard  on  several  large  fills  averaged  six  to  eight 
cents  including  all  costs  of  plant,  etc.  The  cost  of  the  plant 
in  the  above  instance  was  SI 0,000. 

COSTS. 

Figs.  255-263  show  graphically  the  cost  per  foot  of  width 
and  amount  of  materials  required  per  foot  of  width,  for  dif- 
ferent types  of  dam.  Figs.  255  and  256  refer  to  the  type  of 
dam  shown  in  Fig.  213  and  give  respectively  the  quantity  of 
material  and  cost  for  different  heights  of  dam.  Figs.  257  and 
258  refer  to  the  type  of  dam  shown  in  Fig.  214  and  give  re- 
spectively the  cost  and  the  quantity  of  material.  Figs.  259 


HYDRAULIC  CONSTRUCTION. 


275 


(M 


-%o ^ &T  so  *x>  std 

v^cmcfe 

FIG.  255. 


so 


tOoMar^i 

FIG.  256. 


FIG.  257. 


276 


HYDROELECTRIC  PLANTS. 


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Thousand  of  feet 
FIG.  258. 


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FIG.  259. 


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FIG.  260. 


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600       roo       BOO      900 


HYDRAULIC  CONSTRUCTION. 


277 


/ooo 


900C — 600- 


I 


FIG.  261. 


£O  /OO 

//e/gftf  of  Darn  fn 

FIG.  262. 


54 


oo  90 


jus  /•yo 


of  Dam  //? 
FIG.  263. 


278 


HYDROELECTRIC  PLANTS. 


and  260  show  the  cost  of  building  and  the  amount  of  steel  re- 
quired for  reinforced  concrete  dams  of  the  gravity  type,  built 
respectively  for  low  and  high  heads.  Figs.  261,  262,  and  263 
show  cost  data  for  low  solid  concrete,  high  solid  concrete,  and 
high  concrete  steel  dams  respectively.  These  costs  do  not  in- 
clude foundations. 

ABUTMENTS. 

Where  the  dam  is  on  soft  bottom  and  rests  upon  a  mat, 
the  abutment  should  in  all  cases  stand  on  the  same  mat.  The 
more  weight  on  the  mat  the  better. 


FIG    264. 


The  earth  fill  behind  the  abutments  must  be  put  in  with  great 
care.  The  earth  should  be  selected  and  tamped  in  six-inch 
layers  well  wet  down.  Fig.  264  gives  the  amount  of  material 
in  solid  concrete  abutment  shown  in  Fig.  265. 

The  reinforced  concrete  abutment,  Fig.  266,  is  much  cheaper 
and  better.  The  plan  view  of  the  solid  abutment  shows  the  wing 
is  given  a  turn  up  stream.  The  object  of  this  is  to  form  a  pocket 
so  that  any  leakage  is  stopped  by  the  earth  falling  into  the 
corner.  If  a  liberal  wing  is  not  provided  and  of  this  shape 
there  will  always  be  a  leak  along  the  abutment.  The  reinforced 
abutment  has  so  many  wings  that  the  pocket  is  not  necessary. 
Fig.  267  gives  the  amount  of  material  used  in  the  abutment 
shown  in  Fig.  266. 


H YDRA  ULIC  CONSTR UCTION. 


279 


280 


HYDROELECTRIC  PLANTS. 


•">"^^ 


FIG.  2GG. 


Cubic  terete  of  Concrete 
FIG.  267. 


HYDRAULIC  CONSTRUCTION. 


281 


FLASHBOARDS. 

The  height  of  a  dam  is  only  limited  by  the  value  of  the  over- 
flowed lands,  and  as  it  is  usually  only  during  high  water  that 
the  lands  are  damaged,  the  height  of  the  dam  in  summer  is 
lower  than  is  actually  necessary.  It  is  to  increase  the  height 
of  the  dam  during  low  water  (just  when  head  is  most  needed) 
that  the  dashboard  is  used.  There  has  never  been  a  flashboard 
designed  that  suited  all  requirements  and  yet  its  value  is  so 
great  that  most  dams  are  equipped  with  some  one  of  the  various 
varieties. 

One  of  the  simplest  forms,  see  Fig.  268,  has  proved  the  most 
satisfactory.  It  consists  of  wooden  or  iron  posts  set  into  the 
crest  of  the  dam  and  supporting  vertical  planks  against  the 
water  pressure.  The  posts  are  so  designed  that  when  the 


-      rr _ —       f/ 

ITr 


FIG.  268. 

water  exceeds  a  certain  amount  they  break  off  and  plank  and 
posts  go  down  stream.  The  planks  are  fastened  to  the  posts 
by  means  of  staples  through  which  pass  the  posts,  otherwise, 
when  the  water  was  drawn  down  below  the  crest  of  the  dam 
the  plank  would  fall  off. 

In  calculating  the  dimensions  of  posts,  First  find  the  pressure 
against  the  post.  P  =62.5  H  (Ii/2  +  h)  (Fig.  263),  in  the  case 
where  the  water  flows  over  the  boards  at  a  depth  h\  and  P  = 
i  7/X62.5XH  when  it  comes  to  some  depth  H,  at  or  below  the 
top  of  board.  Having  P,  the  moment  of  pressure  against  the 
post  is  found  by,  PXl  =  inch  pounds  =  M.  I  is  found  where 

water  flows  over  the  boards  by  /  =  —  (l-f-  77 — r-p )  and     for 

o  \        H  +  2  h  I 

water  at  top  of  boards  /  =  H/3.     /  must  be  given  In  inches. 
Having  determined  the  permissible  height  of  water  over*the 


282  HYDROELECTRIC  PLANTS. 

boards,  find  the  moment  of  pressure  for  that  height  and  then 
for  the  water  at  the  top  of  the  board. 

The  resisting  moment  of  the  post  M  is  then  found  for  both 
cases,  as  follows:  Let  s  =  the  safe  strength  per  square  inch  of 
the  post.     Then  if  post  is  of  round  section 
M  =  .  098  +  s  +  d* 

See  properties  of  sections  page. 

For  example:  A  flashboard  three  feet  high  and  posts  of  round 
white  pine  and  three  feet  between  centers  with  a  depth  of  not 
more  than  12  inches  of  water  over  the  boards;  find  the  diameter 
of  the  post. 

First,  when  water  is  12  inches  deep  over  boards,  P  =  62.5X3 


r+l     =    469    pounds    per    foot    length    or    469X3  =  1407 

pounds  pressure  against  one  post.     This  pressure  P  acts  at  a 

3  /  1    \ 

height  of--  I    1+  .TT-O)  =  1.2  fee  tor  14.  4  inches  from  the  bottom. 
o   \  tj-r  Z/ 

Therefore  the  moment  of  pressure  against  the  post  is 

M  =  14.4  X  1407  =  20,261  inch  pounds. 
Second,  when  the  water  is  at  top  of  boards: 

p  =  |  x  62.5X3  =  281  pounds  per  foot 
ft 

or 

28iX  3  =  843  pounds  on  post. 

/   =  |  =  1  foot  =  12  inches. 
o 

The  moment  of  pressure  is 

M'  =843X12  -  10,116  inch  pounds. 
The  moment  of  posts'  resistance  in  the  first  case  is 

M=  .098  xs  x  d3 

If  we  take  s  =  3200  as  the  breaking  strength  of  white  pine  and 
substitute,  we  have 

.098X3200  d3  =  20,261    and   d5  =  >d  ==  4-  in- 


With  water  at  top  of  board  3200  d3  x  .098  =  10,116;  d=  3.2  in. 


HYDRAULIC  CONSTRUCTION.  283 

inches.  Therefore,  the  post  should  be  slightly  more  than  3  inches 
in  diameter.  From  this  it  is  seen  that  the  posts  will  be  safe  with 
water  at  top  of  the  boards,  but  will  break  when  the  water  is 
a  few  inches  above,  as  Table  53  gives  the  breaking  strength  of 
white  pine  as  4000  pounds  square  inch.  For  square  posts 


After  a  few  seasons  of  actual  test  the  exact  size  of  the  posts 
will  have  been  determined. 

The  loss  of  the  boards  in  most  cases  is  of  small  moment  as 
the  dam  is  only  a  few  hundred  feet  long,  and  in  many  cases  the 
plank  can  be  caught  below.  However,  the  posts  do  not  always 
break  at  the  right  time,  often  breaking  too  soon  and  causing  a 
waste  of  water.  They  may  also  concentrate  the  current  where 
a  few  posts  have  broken  prematurely,  thus  causing  uneven 
wear  on  the  dam  crest. 

In  the  plans  for  the  Yorktown  dam  Fig.  300  is  shown  a  form 
of  flashboard  designed  by  the  author.  It  is  especially  adapted  to 
short  dams,  though  it  can  be  applied  to  any  length.  By  turning 
the  shaft  all  the  posts  are  lowered  or  raised  at  the  same  time.  In 
lowering,  however,  as  the  top  of  the  posts  get  below  the  center 
of  the  first  plank,  that  plank  tips  over  and  goes  down  stream. 
As  the  tops  come  to  the  centers  of  the  next  plank  they  also 
pass  over  and  so  on  with  as  many  planks  as  the  boards  are 
high.  After  the  flood  has  subsided  it  is  an  easy  matter  for  a 
man  to  walk  out  on  the  crest  and  place  new  boards. 

Such  flashboards  are  seldom  over  three  feet  high  though  they 
have  been  built  four  feet. 

Quite  a  severe  vacuum  forms  under  the  water  sheet  and 
unless  air  inlets  are  provided  the  posts  will  fail  much  sooner 
than  the  above  calculations  would  indicate. 

A  form  of  flashboard  patented  by  J.  H.  Shedd  and  O.  P.  Sarle 
is  shown  in  Figs.  269  to  270.  These  were  used  at  Norwich, 
Conn.,  on  a  dam  432  feet  long  and  have  apparently  given  sat- 
isfaction 

Referring  to  Fig.  270  the  board  m  is  pivoted  on  a  toothed  cam 
roller  e.  The  object  of  e  is  to  vary  the  center  of  resistance  to 
suit  the  varying  center  of  water  pressure  due  to  an  increasing 


284 


HYDROELECTRIC  PLANTS. 


now  of  water  over  the  boards.  With  the  water  at  the  top  the 
center  of  water  pressure  is  slightly  below  the  teeth  then 
in  contact.  As  the  flood  comes  on,  the  center  of  pressure 


FIG.  270. 


rises  and  gradually  tilts  the  gate  until  when  the  water  has 
reached  a  certain  stage  it  lies  in  a  horizontal  position  resting 
on  the  Z  bar  g,  which  runs  full  length  of  the  dam.  As  the 


HYDRAULIC  CONSTRUCTION. 


285 


flood  recedes  the  boards  automatically  resume  their  normal 
position.  Fig.  270  is  a  view  of  the  entire  flashboard  mounted 
on  the  dam,  and  Fig.  269  a  detail  of  one  section  of  flashboard. 
While  possessing  some  very  valuable  features  this  form  has 
certain  defects.  There  are  a  great  many  obstructions  for  drift 
wood  to  strike  against  and  lodge  upon.  It  gives  the  water  a 
perpendicular  fall  upon  the  dam,  causing  heavy  vibrations. 
There  is  a  serious  liability  to  damage  from  ice  floes  and  heavy 
logs.  All  the  sections  do  not  assume  the  same  relative  position 
at  all  stages  of  flood  water.  There  is  some  leakage  between 
the  sections,  etc. 


FIG.  272. 

Fig.  272  shows  a  mechanism  invented  by  S.  C.  Irwan  and 
A.  M.  Bournan  which,  though  more  especially  meant  for  a  mov- 
able dam,  is  well  adapted  for  flashboards.  The  part  u  is  in 
the  form  of  the  sector  of  a  circle,  is  hollow  and  extends  either 
the  full  length  of  the  dam  or  in  long  sections.  The  sector  u 
floats  upon  the  water  admitted  into  the  chamber  x  when  it  is 
wished  to  elevate  the  crest,  any  water  contained  within  u  being 
pumped  or  drained  out  through  the  pipe  a.  To  lower  the  crest, 
water  is  let  out  of  x  and  pumped  or  admitted  into  u  causing  u 
to  settle  down.  This  form  of  flashboard  may  be  made  of  any 


286 


HYDROELECTRIC  PLANTS. 


height,  the  limitations  being  the  permissible  widening  of  the 
crest  of  dam  and  the  factor  of  safety  of  the  dam  under  the 
increased  head.  The  top  slope  of  the  sector  affords  a  good  spill- 
way for  the  water  and  there  are  no  projections  for  the  lodgment 
of  trash  or  to  cause  vibrations.  The  joints  can  all  be  made 
practically  water-tight  and  the  entire  mechanism  may  be 
raised  or  lowered  at  any  time  from  the  shore  by  merely  operating 
the  air  and  water  valves. 


FIG.  273. 

The  water  pressure  against  this  form  of  flashboard  is  hori- 
zontal, and  in  applying  it  to  dams  must  be  allowed  for  in  the 
design  of  the  structure. 

Fig.  273  shows  a  form  of  flashboard  which  possesses  the  con- 
trolling features  of  Fig.  270  and  the  principal  of  Fig.  272.  Fig. 
273  shows  it  adapted  to  the  timber  dam,  and  this  particular 
board  raised  the  water  three  feet.  The  board  C  is  all  in  one 
length  and  bolted  together  with  one-inch  bolts.  It  is  pivoted 
on  the  bronze  trunions  H.  Every  four  feet  along  the  crest  is  a 
bearing  which  bears  on  the  pivot  H.  The  pivot  is  supported 


HYDRAULIC  CONSTRUCTION. 


287 


by  the  timber  A.  The  deck  planks  M  have  a  small  crack 
left  between  them  so  that  the  water  pressure  has  free 
access  to  the  chamber  R.  About  20  feet  apart  are  the  valves 
L  which  are  operated  by  means  of  a  steel  cable  from  the  shore. 
With  the  valves  shut  the  gate  is  as  shown,  but  when  these  are 
open  the  water  pressure  on  the  left  hand  side  of  the  board  causes 
it  to  assume  the  position  shown  dotted.  During  ice  flows  or 
very  high  water  the  board  is  let  down  leaving  a  clear  crest  for 
the  passage.  When  up  this  flashboard  will  leak  no  water,  and 
when  down  leaves  nothing  for  objects  to  strike  against  or  lodge 
upon. 

Fig.  222  shows  the  same  type  of  flashboard  used  on  a  masonry 
dam.  Spaced  at  intervals  across  the  length  of  dam  are  beams 
A  pivoted  on  a  shaft  or  trunion  B.  Riveted  to  the  top  of  these 


FIG.  274. — Drum  Dam. 

beams  is  the  wood  or  steel  decking.  A  steel  plate  C  bent  to  the 
proper  circle  is  attached  to  angle-iron  imbedded  in  the  masonry. 
D  is  a  floor  covering  the  chamber  E,  its  only  purpose  being  to 
exclude  stones,  sticks,  etc.,  which  might  interfere  with  the 
operation  of  the  leaf  A.  It  is  provided  with  sufficient  openings 
to  supply  the  chamber  with  water.  The  operation  then  is  as 
follows:  The  water  pressure  has  free  access  to  the  entire  surface 
of  the  movable  deck  and,  with  the  water  even  with  the  crest  G, 
the  center  of  this  pressure  P  is  one -third  the  depth  from  the 
edge  F  to  the  surface  and  strikes  the  deck  at  P.  As  the  water 
rises,  P  also  rises  till  with  the  water  six  feet  above  the  level  H, 
it  arrives  at  Pr.  P'  travels  rapidly  along  toward  G,  after  it 
passes  B,  permitting  of  very  accurate  adjustment.  By. making 


288 


HYDROELECTRIC  PLANTS. 


F  B  may  be  more  nearly  horizontal  if  for  mechanical  reasons  it 
is  so  desired. 

If  it  is  desired  to  control  the  movement  from  the  shore  the 
web  H,  the  Tee -iron  7  and  valve  N  are  added,  the  web  and  Tee -iron 
making  a  more  or  less  perfect  shut-ofT  of  the  water,  so  that  by 
pumping  water  into  the  space  L  under  the  deck,  the  pressure  P 
is  reduced  to  zero  and  the  crest  will  fall.  If  necessary,  by 
pumps,  the  pressure  in  L  may  be  made  to  exceed  P. 


FIG.  275. 

If  thought  necessary,  a  steel  apron  M  (shown  dotted)  may  be 
hinged  to  the  crest  to  form  a  spillway. 

This  mechanism  is  suited  to  almost  any  range  of  variation 
in  water  levels,  and  may  serve  equally  well  as  a  movable  dam. 
It  may  also  be  applied  to  the  gravity  dam  as  the  component  of 
the  water  pressure  may  be  made  to  act  as  nearly  vertical 
as  desired.  In  the  design  shown  the  range  of  movement  was 


HYDRAULIC  CONSTRUCTION.  289 

3J  feet  and  necessitated  a  width  of  crest  of  19  feet.  By  making 
the  beam  A  straight  the  crest  could  be  narrowed  somewhat. 
The  vacuum  which  forms  underneath  at  0  will  help  in  actuating 
the  leaf  since  for  a  thin  sheet  of  water  over  the  crest  it  will  be 
slight  and  for  a  heavy  overpour  quite  severe.  By  controlling 
this  vaccuum  with  suitable  inlet  pipes  it  may  be  increased  when 
it  is  desired  to  lower  the  crest,  thus  sucking  it  downward.  A 
float  may  be  used  to  open  the  vacuum  inlet  automatically  at  a 
certain  stage  of  the  water,  and  if  necessary,  start  the  pumps. 

Fig.  275  illustrates  what  is  perhaps  the  most  unique  and  heavy 
of  all  movable  dams  or  flashboards.  It  was  built  in  the  city 
of  Schweinfurt,  on  the  river  Main,  Germany.  At  this  place 
the  law  forbade  any  structure  being  placed  in  the  river  bed 
above  a  certain  height  and  it  was  to  gain  the  permit,  that  this 
mechanism  was  designed.  An  e-xperimental  dam  was  put  in 
operation  having  a  cylinder  13J  feet  in  diameter  and  59  feet 
long  and  it  gave  perfect  satisfaction.  The  one  shown  is  6J  feet 
in  diameter  and  114  feet  long.  The  steel  shell  is  1.1  inch  thick 
and  weighs  193,600  pounds.  This  clyinder  is  lifted  to  a  height 
of  13  feet  by  means  of  an  18  horse-power  electric  motor  and 
may  also  be  operated  by  12  men  in  which  case  it  takes  three 
hours  to  lift. 

The  concentric  cylinder  C  is  filled  with  water  when  the  cylinder 
is  down  to  give  added  weight,  but  as  it  turns  in  raising  this 
water  spills  out. 

The  lifting  is  all  done  at  one  end  but  at  each  end  there  is  a 
cog  wheel  and  rack. 

HEAD  GATES. 

What  the  safety  valve  is  to  the  steam  engine,  the  head  gate 
is  to  the  water  power.  Every  water  power  should  possess  such 
a  safety  device,  for  there  comes  a  time  in  the  history  of  every 
water  power  when  it  is  desired  to  empty  the  head  race,  flumes, 
etc.,  of  water  and  it  is  at  such  times  that  a  reliable  head  gate 
is  wanted.  As  the  office  of  the  head  gate  is  to  protect,  it  should 
be  placed  at  the  very  entrance  of  the  head  race. 

The  form  shown  in  Fig.  276  is  one  of  the  most  common  and 
we  think  the  best.  The  fill  a  is  made  wide  enough  to  form  a 
roadway  and  heavy  enough  to  resist  the  overturning  force  of 
the  water.  When  the  bottom  is  soft,  this  form  of  head  gate 


290 


HYDROELECTRIC  PLANTS. 


is  placed  upon  a  mat  the  same  as  a  gravity  dam.  In  nearly 
every  case,  one  row  of  sheet  piling  should  be  driven  along  the 
up-stream  edge  of  the  mat  used  under  head  gates.  The  length 
%  should  generally  be  about  equal  to  the  depth  of  the  water. 
The  ends  of  the  head  gates  should  be  well  protected  against  the 
water  cutting  around  and  the  down-stream  wings  (Fig.  276) 
should  be  extended  well  down  stream  to  prevent  the  wash  of  the 
water  after  it  has  passed  through  the  gates. 

A  velocity  of  200  to  300  feet  per  minute  may  be  allowed  to 
the  gates  as  the  up  and  down  stream  length  is  so  small  that  the 
loss  of  head  will  be  inappreciable.  Where  the  banks  are  a 
sandy  loam,  or  other  easily  washed  material,  every  joint  must 
be  water  tight.  A  good  plan  is  to  sheet  all  wooden  bulkheads 


I//// 


FIG.  276. — Head  gates. 

exposed  to  hydraulic  pressure  with  "  all  heart  "  yellow  pine 
flooring.  In  the  last  described  head  gate,  all  parts  above  water 
and  for  a  foot  or  so  below  should  be  of  concrete  or  masonry 
as  the  wood  at  the  water  line  decays  rapidly.  The  piers  can 
also  be  of  masonry  or  concrete  in  which  case  greater  permanence 
is  secured. 

On  large  work  the  head  gate  frequently  reaches  heavy  pro- 
portions. Fig.  277  gives  a  design  for  a  gate  20x50  feet.  In 
this  design  the  gate  proper  weighs  about  66,500  pounds,  and  to 
balance  this,  a  counter  balance  A  is  used.  The  counter  balance 
consists  of  a  box  girder  50  feet  long  and  having  a  space  24  inches 
by  42  inches  by  50  feet  inside,  which  is  filled  with  concrete,  thus 
giving  the  necessary  66,500  pounds.  The  chain  at  each  end  of 
gate  passes  over  a  wheel  B,  the  links  fitting  into  the  rim  similar 


HYDRAULIC  CONSTRUCTION. 


291 


FIG.  277. 


292 


HYDROELECTRIC  PLANTS. 


to  a  chain  hoist.  To  operate  the  gate  the  hand  wheel  C  is  turned 
until  the  eccentrics  lift  the  gate  away  from  the  bearing  on  the 
pier.  This  throws  the  pressure  on  the  eight  wheels  and  makes 


FIG.  278. 

the  lifting  of  the  gate  by  means  of  the  worm  gear  D,  an  easy 
matter. 

The   horizontal   down   stream   thrust   on   the   gate   is   about 


FIG.  279. — Common  head  gates. 

630,000  pounds.  Therefore  the  piers  E  must  weigh  4/3  of 
630,000  or  840,000  pounds  to  be  in  equilibrium  against  sliding 
and  twice  that  for  a  factor  of  safety  of  two.  In  the  design  given 


HYDRAULIC  CONSTRUCTION. 


293 


this  factor  is  attained.  In  almost  all  cases  instead  of  having 
some  means  of  throwing  the  pressure  on  the  wheels,  a  small 
gate  would  be  provided  to  let  in  the  water  slowly  and  thus 
takeoff  the  pressure,  but  sometimes  this  is  not  desired  as  when 
it  is  necessary  to  control  the  water  and  limit  the  amount  supplied 
to  the  canal.  On  the  Chicago  drainage  canal  and  the  great 
power  at  St.  Mary's  river,  gates  similar  to  the  one  shown  are 


FIG.  280. 

used  for  this  purpose.     The  cost  of   this  gate   would   be   about 
$8000  all  complete. 

Fig.  278  shows  a  common  type  of  head  gate  suited  to  heads 
up  to  20  feet.  Fig.  279  shows  the  most  common  head  gate 
and  one  which  is  plenty  good  enough  for  all  ordinary  circum- 
stances. The  stem  a  should  be  made  of  an  8x8-inch  or  a  6x8- 
inch  timber.  The  planks  e  should  be  seasoned  and  edged. 
The  braces  c  are  nailed  on  and  the  stem  is  bolted  with  f-inch 


294 


HYDROELECTRIC  PLANTS. 


carriage  bolts.  The  guides  for  the  gates  should  be  as  at  E 
and  not  as  at  D  on  account  of  the  liability  of  weeds  and  sticks 
getting  caught  and  causing  the  gate  to  bind.  This  gate  may 
have  two  stems  where  the  area  is  great  or  the  head  high. 

The  hoists  shown  in  Figs.  280  to  282  are  suited  to  this  gate; 
Fig.  282  being  used  for  all  the  gates  of  a  series  except  the  one 
used  to  raise  whrle  the  full  pressure  is  on. 


FIG.  281. 

For  gates  under  high  heads  (40  to  100  feet),  the  type  shown 
in  Fig.  283  is  used.  For  larger  gates  and  heads  of  30  to  50  feet 
the  hoist  shown  in  Fig.  280  may  be  employed. 

The  elements  of  the  design  of  gates  is  given  below.  The 
force  necessary  to  lift  is  found  as  follows:  According  to 
usual  practice  the  friction  between  oak  and  iron  is  about  62 


HYDRAULIC  CONSTRUCTION. 


295 


per  cent.  That  is,  it  will  take  62  per  cent,  of  the  water  pressure 
against  the  gate  to  keep  the  gate  moving.  Assuming  for 
example  a  bronze  gate  2£  feet  by  2J  feet  working  on  bronze 
guides  under  a  head  of  30  feet,  the  horizontal  pressure  will  be 
62.5x29x6.25  =  11,325  pounds;  25  per  cent,  of  this  (for 


FIG.  282. 


bronze  on  bronze)  =  2831  pounds,  which  is  the  force  required 
to  move  the  gate.  General  Morin  states  that  it  requires  about 
one-eighth  more  force  to  start  the  gate,  therefore  to  be  safe, 
3200  pounds  will  be  taken  as  the  starting  force.  Now  suppose 


FIG.  283. 

the  gate  weighs 500  pounds 

Friction  of  screw  =  (500  +  7021)  Xcoefficient  .25. . .  1880 
Equivalent  weight  of  gate  due  to  friction  11.325X 

.25 3200 

Friction  of  nut  =  (500  +  7021)  Xcoefficient  .15 1128 

Total  equivalent  weight,  W  = 6708 


296 


HYDROELECTRIC  PLANTS. 


Now  for  the  hoist  shown  in  Fig.  283  when  the  hand  wheel  is 
24  inches  in  diameter  and  the  pitch  of  the  screw  on  the  stem 


is  1  inch,  W  = 


F  X       *  R 


where    W  =  6708;  F  =  force    re- 


quired to  start  gate;  R  =  radius  of  hand  wheel  =12  inches; 
P  =  1. 

Substituting,  F  =  890  pounds. 

This  is  too  large  for  a  hand  wheel  and  such  a  gate  would  be 
lifted  with  two  such  screws  or  a  set  of  gears  would  be  used  to 
reduce  the  required  pressure,  as  in  Fig.  280. 

SLUICE  GATES. 
In  Fig,  284  a  very  common  form  of  umbrella  waste  gate  is 


FIG.  284, 

shown.  This  gate  is  often  made  a  part  of  the  dam.  The  size 
shown  is  that  usually  selected,  there  being  as  many  gates  dis- 
tributed along  as  thought  necessary  to  pass  the  water.  As  here 
shown,  the  down  stream  thrust  of  the  water  is  horizontal  and 
heavy  masonry  walls  arc  necessary  to  resist  it.  The  plan  shown 


HYDRAULIC  CONSTRUCTION. 


297 


in  the  Noblesville  plant  (Fig.  352)  throws  most  of  the  pressure 
in  a  vertical  direction.  Experiments  made  by  the  author  on 
old  head  gates  show  that  F  is  about  85  per  cent,  of  the  hori- 
zontal pressure  against  the  gate. 

Fig.  285  shows  a  hydraulically  operated  gate.  This  gate  is  about 
the  best  of  all  the  types  where  some  form  of  power  is  available 
at  the  power  house  at  all  times.  Usually  when  it  is  required 


FIG.  285. 


to  operate  the  gates  it  is  for  the  purpose  of  a  shut-down,  and 
therefore  the  power  ceases.  When  there  is  a  storage  battery 
plant  or  where  current  can  be  brought  to  the  power  house  from 
some  other  plant,  a  motor  can  be  used  to  drive  a  force  pump. 
Pressures  of  500  to  1000  pounds  per  square  inch  should  be  used. 
The  piston  rod  will  not  require  packing  or  piston  rings  as  some 
waste  of  water  during  the  lift  will  do  no  harm.  The  valve  a 
lets  the  water  in  on  one  side  and  out  on  the  other,  and  by  pulling 
on  the  cord  b,  the  water  will  be  admitted  to  either  side  of  the 
piston. 


298 


HYDROELECTRIC  PLANTS. 


HEAD  RACKS. 

As  the  uninterrupted  working  of  the  plant  depends  largely  on 
keeping  driftwood  and  other  objectionable  trash  out  of  the 
turbines,  it  becomes  of  the  first  importance  to  properly  con- 
struct the  racks.  In  a  large  majority  of  cases,  their  area  is 
made  much  too  small,  due  allowance  not  being  made  for  the 
area  occupied  by  the  rack  bars.  The  net  area  of  the  rack  should 
be  such  that  not  more  than  40  to  60  cubic  feet  of  water  per 
minute  will  pass  per  square  foot  of  area.  The  cheapest  form 
of  rack  bars  are  those  made  as  shown  in  Fig.  286. 

The  bars  a  should  be  from  one  to  three  inches  apart  depending 
on  the  size  of  turbine  they  are  to  protect  and  should  be  built 
in  sections  of  say,  from  six  to  eight  bars  held  together  by  J-inch 


bate 


FIG.  286. 

bolts  b.  The  sections  are  not  fastened  to  the  rack  frame  and 
so  may  be  easily  removed  for  repairs.  If  the  length  of  the  bars 
is  not  over  ten  feet  the  brace  B  is  unnecessary.  Iron  is  much 
the  best  material  for  the  bars,  and,  though  the  first  cost 
is  somewhat  more  than  for  wood,  it  will  be  found  the  cheapest 
in  the  long  run.  The  bars  may  be  of  iron  from  Jx2  inches 
to  |x4  inches.  For  heads  of  from  6  to  14  feet  the  use  of  f  x3-inch 
iron  strengthened  every  six  feet  of  its  length  by  a  J-inch  bolt, 
is  advised,  a  piece  of  f-inch  gas  pipe  should  be  strung  on  between 
each  pair  of  bars  for  spacers. 

There  should  be  two  racks,  one  a  coarse  rack  above  the  other. 
The  coarse  rack  should  have  3-inch  spaces  between  the  bars 
and  the  fine  rack  1  inch  to  1J  inch.  For  small  turbines  under 
15  inches  a  brass  wire  screen  affords  excellent  protection.  The 


HYDRAULIC  CONSTRUCTION. 


299 


meshes  should  be  f ,  f ,  or  f  inch  square.  Instead  of  the  second 
coarse  rack  a  deflecting  boom,  a,  may  be  used  (Figs.  286  and  287). 
Several  buoyant  timbers  are  strung  together  across  the  head 
race  as  shown,  the  bars  being  given  a  slant  towards  the  dam 
and  projecting  down  into  the  water  several  feet.  Such  a  boom 
will  catch  a  large  proportion  of  the  trash  and  most  of  it  will 
glance  off  and  pass  over  the  dam. 


FIG.  287. 

TABLE  XXXVIII. 
WEIGHT  OF  ONE  SQUARE  FOOT  OF  RACK. 


Size  of  Bar  and  Weight 
of  One  Bar  per  Foot. 

Distance  Between  Bars. 

I" 

1" 

iF 

H" 

1J" 

2" 

2*" 

3" 

4" 

i"x3"         2.55  Ibs. 

30.6 

24.5 

20.5 

17.5 

15.3 

13.6 

I"  x3"         3.83  Ibs. 

41. 

33.4 

28.3 

24.5 

21.7 

19.5 

16. 

\"  x  4"         6.8  Ibs. 

40.8 

36.25 

30. 

27.25 

23.4 

18 

Rack  bars  cost  about  three  cents  per  pound. 

Anchor  ice  is  the  worst  foe  to  the  head  rack  and  has  been 
known  to  render  a  valuable  water  power  practically  useless 
during  the  winter  months.  The  cause  of  anchor  ice  is  a  much 
disputed  question,  but  it  is  the  belief  of  the  writer  that  it  is 
formed  by  the  coagulation,  as  it  were,  of  the  water  as  it  passes 
from  a  pool  of  comparatively  quiet  water  over  a  shoal  or  rapid. 
When  water  freezes  on  the  pond,  a  certain  amount  of  the  air 
is  imprisoned  in  the  ice  making  its  specific  gravity  less  than  that 
of  water  but  when  the  water  has  been  quiet  and  the  tempera- 
ture below  freezing,  the  water  assumes  a  temperature  below 
freezing  and  yet  does  not  congeal  until  it  is  agitated  on  the 
rapids  where  it  instantly  freezes  and  contracts  into  solid  pasty 
ice  slightly  heavier  than  water,  so  that  it  drifts  along  at  all 


300  HYDROELECTRIC  PLANTS. 

depths  and  finally  lodges  against  the  racks  much  to  the  disgust 
of  the  power  user. 

However,  if  proper  precautions  are  taken,  shut-downs  will 
never  be  found  necessary  on  that  account.  At  Norfolk,  on 
Raquette  River,  the  Remington  Paper  Co.  overcame  the  diffi- 
culty, which  at  first  seemed  serious,  by  building  a  house  over 
the  rack  and  keeping  it  warm.  Men  were  also  kept  at  work 
with  rack  hooks  cleaning  out  the  anchor  ice.  In  Fig.  288  a 
sketch  of  a  patent  rack  is  shown  which  gives  complete  protection 
against  every  head  rack-  ill. 


FIG.  288. 

The  rack  is  made  in  6-foot  sections.  The  wire  netting  a  is 
such  as  is  used  for  reinforcing  concrete  and  is  caused  to  run 
over  the  steel  rack  bars  b  by  means  of  the  friction  drum  C. 
The  netting  may  be  made  to  run  as  slowly  as  desired  and  only 
runs  when  it  is  found  necessary  to  clear  the  rack. 

A  rack  similar  to  this  was  used  at  the  Mill  Creek  power,  only 
it  was  caused  to  revolve  by  means  of  a  current-wheel  placed 
behind  the  rack  and  in  the  penstock. 


CHAPTER  VI. 


POWER  HOUSE  CONSTRUCTION. 

Together  with  head  gates,  racks,  penstocks,  etc.,  the  accesso- 
ries to  the  power  house  have  been  treated,  some  of  them  being 
at  times  a  part  of  it.  The  power  house  proper,  however,  is 
the  subject  of  this  chapter. 

FOUNDATIONS. 

There  is  no  one  thing  more  important  in  all  building '  opera- 
tions than  the  foundations.  After  the  soundings  have  been 
properly  made,  it  should  be  an  easy  matter  to  design  the  founda- 
tions, and  yet  how  few  heavy  buildings  are  there  which  do  not 


FIG.  289. 

settle  and  show  cracks.  Most  of  the  skyscrapers  of  Chicago 
are  steadily  sinking,  as  are  also  those  of  New  Orleans.  This  is 
to  be  expected  on  such  foundation  material  as  those  cities  have, 
but  the  architect  shows  his  skill  by  so  designing  the  foundations 
that  a  20-story  building  always  remains  plumb  no  matter  how 
much  it  may  settle.  Building  a  power  house  on  the  bank  of  a 
river  introduces  a  little  problem  in  foundations. 

Fig.  289  shows  a  power  plant  the  flume  of  which  rests  on  the 
solid  hardpan  eight  feet  below  tail  water.  The  power  house 
containing  the  generators  extends  back  on  to  the  bank  and 
rests  on  gravel.  Also  see  Fig.  47. 

301 


302 


HYDROELECTRIC  PLANTS. 


Now,  if  special  provision  is  not  made  to  give  the  base  of  the 
power  house  foundations  sufficient  area,  there  will  be  a  crack 
at  a  as  shown.  The  flume  will  not  settle  but  the  generator  house 
will. 

Abutments  resting  on  mats,  and  heavy  wing  walls  running 


FIG.  290. 

back  into  the  shore  are  also  subject  to  cracks  unless  carefully 
designed.  Safe  pressures  for  foundations  are  given  on  page  124. 
All  soils  will  settle  some,  therefore  the  pressures  must  be  met 
with  sufficient  bearing  surface  in  the  foundations. 


FIGS.  291,  292. 

For  heavy  concrete  power  houses  four  feet  of  firm  soil  under 
the  base  is  sufficient,  especially  wThen  placed  on  a  mat  as  in 
Fig.  290.  Wet  sand  will  sustain  almost  any  load  if  it  is 
held  in  place  by  sheet  piling.  The  mat  M  should  make  a  close 
fit  with  the  piling  but  not  be  fastened  to  it.  In  this  case  the 


POWER  HOUSE  CONSTRUCTION.  303 

strata*  of  clay  need  only  be  about  a  foot  thick  as  the  pressures 
are  evenly  distributed  over  it  by  the  sand  above.  To  pre- 
vent the  piling  from  spreading,  strap  iron  anchors,  5,  are  bolted 
to  the  wales  and  to  the  mat  as  shown.  This  permits  settling 
of  the  mat. 

Where  heavy  loads  are  to  be  borne  on  columns  the  arrange- 
ment shown  in  Fig.  291  may  be  employed.  The  concrete  must 
be  of  rich  mixture. 

For  engine  foundations  where  it  is  desired  to  avoid  all  vibra- 
tions the  pier  is  placed  on  a  bed  of  clean  dry  sand.  As  long 
as  no  sand  is  allowed  to  escape  the  pier  will  not  settle,  and  to 
make  this  sure  a  copper  sheet  a  should  be  embedded  as  shown, 
Fig.  292. 

The  heavier  the  foundations  the  less  the  vibration.  About 
300  pounds  of  foundation  per  one  horse-power  is  good  practice 
for  engines  up  to  25  horse-power,  200  pounds  25  to  100  horse- 
power, and  175  pounds  for  those  of  100  to  5*00  horse-power. 
Of  course  this  only  applies  to  foundations  on  soft  shaky  soils. 
The  safe  bearing  pressures  per  square  foot  of  the  soil  must  not 
be  exceeded  (see  Table  XXXI),  and  this  often  makes  a  foundation 
of  much  larger  base  necessary. 

STRUCTURE. 

There  should  be  only  one  type  of  power  house  and  that  type 
the  best,  but  unfortunately  the  majority  of  the  power  plants  must 
be  built  as  cheaply  as  possible. 

The  flume  is  that  part  which  contains  the  turbine. 
The  cheapest  arrangement  is  that  in  which  the  flume  is  a 
part  of  the  dam.  Figs.  293  and  294  show  two  views  of  such 
a  flume,  built  into  a  gravity  dam.  In  building  this  flume  it 
must  be  remembered  that  a  part  of  the  gravity  virtue  of  the 
dam  is  taken  away  and  a  horizontal  down  stream  push  added, 
therefore  caution  must  be  used  in  bracing  the  down  stream 
bulkhead.  The  plan  shown  is  for  a  30-inch  turbine  taking 
5000  cubic  feet  of  water  per  minute.  If  the  water  is  drawn 
one  foot  below  the  crest  of  the  dam  the  velocity  in  the  flume 
would  be  90  feet  per  minute,  which  is  good  practice.  With 
12  feet  of  water  in  the  flume  the  horizontal  pressure  at  x  =  35,500 
pounds.  A  rod  1J  inches  in  diameter  will  hold  this  and  as  one 
such  rod  is  a  small  item  of  cost,  its  use  is  advised.  Frequently 


304 


HYDROELECTRIC  PLANTS. 


the  down  stream  sill  A  splits  along  the  line  of  mortises  when 
a  rod  is  not  used.  This  arrangement  could  be  used  for  two 
turbines  in  line  with  the  dam,  though  it  would  be  better  to  place 


FIG.  293.— Timber  wheel  pits  at  end  of  dam. 


FIG.  294.— Timber  wheel  pits  at  end  of  dam. 

them  up  and  down  stream.  By  building  a  masonry  pier  be- 
tween the  flume  and  the  dam,  any  number  of  wheels  could 
be  -set,  as  the  masonry  would  resist  the  horizontal  pressure. 


POWER  HOUSE  CONSTRUCTION. 


305 


Two  posts  are  shown  under  the  wheel  setting  at  B.  These  are 
to  support  the  wheel  and  are  slanted  off  to  each  side  of  tail 
race.  All  planks  are  edged  and  seasoned.  The  head  gate 
stems  have  holes  two  inches  in  diameter  bored  to  permit  the 
gates  being  lifted  with  a  bar. 

A  light  frame  house  should  be  erected  over  the  gears.  This 
same  flume  could,  of  course,  be  used  for  horizontal  wheels. 
One  plan  is  to  have  the  shaft  project  through  the  down  stream 


FIG.  295. — Timber  wheel  pits  for  soft  bottoms. 

bulkhead  and  have  a  rope  drive  to  the  machine  back  on  the 
bank. 

Fig.  295  shows  two  views  of  a  timber  flume  built  entirely 
separate  from  the  dam  and  on  a  sand  bottom,  and  Fig. 
296  shows  a  section  of  the  same  flume.  The  wheel  pit  is 
first  dug  and  the  mat  O  laid.  A  concrete  wall  TV  is  built  as 
shown  serving  to  resist  the  pressure  of  the  sand  under  the 
upper  mat  and  also  as  a  deflection  for  the  water  discharged 
from  the  draft  tubes.  The  timber  frame  serving  to  support 


306 


HYDROELECTRIC  PLANTS. 


the  turbines  rests  partly  on  this  wall.  The  down  stream  sill, 
however,  does  not,  and  as  it  would  have  to  sustain  about  37,000 
pounds  of  water,  and  a  center  load  of  about  5000  pounds,  there 
must  be  placed  at  H,  H,  steel  columns.  Four-inch  gas  pipes 
with  large  cast  iron  bearing  plates  will  serve  this  purpose. 

As  shown,  there  are  settings  for  two  turbines,  but  the  same 
plan  may  be  adapted  to  any  number.  Heavy  rods  are  used 
to  take  up  the  larger  part  of  the  horizontal  pressure.  These 
rods  are  anchored  to  the  up  stream  edge  of  the  fore-bay  mat 
by  means  of  bolts  put  in  before  the  sheet  piling  is  driven.  In 
this  plan  the  fore-bay  is  widened  to  give  liberal  rack  area. 
Sheet  piling  should  be  driven  along  both  the  up  stream  edge  and 
the  ends  as  shown.  The  plan  view  shows  how  the  earth  fill 


FIG.  296. 

is  only  carried  around  to  X.  The  wings  C  D  E  F  would  be 
more  lasting  if  made  of  concrete,  which  if  reinforced  and  braced, 
need  only  be  12  inches  thick.  Where  earth  comes  in  contact 
with  wet  timber  decay  is  very  rapid.  Frequently  sound  timber 
will,  under  such  conditions,  rot  out  in  six  years.  The  fore-bay 
mat  must  be  made  water-tight  and  the  piling  bolted  and  ce- 
mented to  it.  Two  thicknesses  of  plank  should  be  laid  on  the 
mat  under  the  wheel  pit. 

The  greatest  difficulty  is  experienced  in  building  a  power  house 
so  that  water  will  not  follow  around  its  sides,  but  the  plan  here 
shown  should  be  safe  from  such  accidents.  All  earth  fills  must 
be  thoroughly  tamped  while  wet. 

Where  there  is  no  danger  from  back  water,  this  plan  may 
be  used  for  horizontal  wheels. 


POWER  HOUSE  CONSTRUCTION.  307 

A  compromise  between  the  all  timber  and  all  concrete  power 
house,  is  shown  in  plan  and  side  elevation  in  Figs.  297  and  298. 
This  is  a  very  good  plan  for  a  power  house  of  moderate  cost. 
The  cost  could  be  further  reduced  by  substituting  timber  for 
the  concrete  end  walls  shown  at  x.  The  only  defect  that  de- 
veloped in  this  plant  was  the  splitting  of  the  sill  as  shown. 
The  use  of  a  IJ-inch  rod  running  through  all  three  flumes  would 
have  remedied  this  weakness.  Each  flume  contains  one  quarter 
turn  35-inch  Morgan  &  Smith  horizontal  turbine. 

This  complete  power  house  with  a  timber  dam  22  feet  high 
and  300  feet  long  cost  $15,000. 

Fig.  299  shows  a  late  design  of  a  concrete  steel  power  house, 
The  design  of  this  power  house  embodies  a  novel  and  very  im- 
portant improvement.  The  waste  gates,  of  which  there  are 
three  for  each,  are  used  to  draw  down  the  head  in  time  of 
flood.  As  shown  here,  the  gates  not  only  serve  to  pass  large 
quantities  of  water,  but  they  also  act  to  increase  the  power  of  the 
turbines  in  times  of  high  back  water.  This  action  is  quite  similar 
to  that  of  a  steam  injector. 

Fig.  300  shows  a  concrete  steel  power  house  of  the  most 
permanent  kind.  On  account  of  being  cramped  for  room 
the  exciters  and  switch  board  are  here  placed  on  a  plat- 
form above  the  generators.  In  reality  the  governors  and 
generators  are  in  the  basement.  It  is  seldom  that  the  at- 
tendant has  to  tend  the  generators,  the  most  of  his  time  being 
spent  with  the  switchboard  and  exciters,  therefore  this  arrange- 
ment is  permissible  under  the  circumstances.  The  battle- 
mented  cornice  shown  on  the  building  is  made  of  building  blocks 
but  below  this  the  building  is  built  on  the  Thatcher  plan.  A 
feature  of  this  plant  is  the  method  of  emptying  the  reservoir. 
That  part  of  the  flume  floor  above  the  head  gates  is  a  continua- 
tion of  the  dam.  At  Y  instead  of  the  usual  foot  boards,  boards 
are  stood  on  end  as  shown,  each  board  having  a  ring  in  the  top 
by  means  of  which  it  may  be  pulled  out.  The  large  window 
shown  at  end  of  generator  room  is  to  admit  the  generators, 
there  being  no  other  way  in  this  case.  The  stairs  are  all 
steel  and  concrete.  The  floor  and  walls  of  the  generator  room 
are  made  water-tight  up  to  the  down  stream  windows  to  keep 
out  the  back  water. 

Fig.  301  shows  the  section  of  a  power  house  which  is  designed 


308 


HYDROELECTRIC  PLANTS. 


POWER  HOUSE  CONSTRUCTION. 


309 


,.. 


F 


310 


HYDROELECTRIC  PLANTS. 


POWER  HOUSE  CONSTRUCTION. 


311 


312 


HYDROELECTRIC  PLANTS. 


POWER  HOUSE  CONSTRUCTION. 


313 


to  waste  the  water  above  the  dam  through  the  wheel  pits. 
Immediately  above  each  draft  tube  a  concrete  wall  c  is  built 
serving  as  a  deflector  and  to  protect  the  draft  tube  from  the 


FIG.  302. 

force  of  the  water  coming  through  the  waste   gates.     Above 
the  waste  gates  this  wall  is  thinned  to  two  feet,  serving  to  support 


FIG.  303. — Excessive  reinforcing. 

the  flume  floor.     At  the  up  stream  end  the  wall  is  only   12 
inches  thick. 

Fig.  302  shows  a  view  of  the  pier  at  A  B. 


314  HYDROELECTRIC  PLANTS. 

The  rack  D  is  of  heavy  steel  and  serves  to  keep  the  trash  out 
of  the  waste  gates.  At  E  is  shown  a  steel  rack  which  need  not 
be  used  if  the  rack  F  has  sufficient  width. 

Fig.  303  shows  one  of  eight  flumes,  each  containing  two  pairs 
of  turbines.  The  head  was  only  20  feet  though  the  heavy  re- 
inforcing would  give  the  idea  of  a  very  high  pressure. 

This  power  house  was  built  to  cost  as  much  as  possible,  and 
does  not  show  good  engineering.  The  arrangement  of  the 
deflectors  is,  however,  very  good.  They  serve  also  as  piers 
under  the  flume  floor.  The  part  showing  through  the  draft 
hole  is  curved  to  deflect  the  water  while  the  up  stream  end  is 
pointed  so  as  to  not  choke  the  discharge  from  the  turbines  above. 

The  "  Soo  "  plant  is  shown  in  Fig.  304.  This  is  the  largest 
low  head  power  plant  in  the  world.  Each  flume  is  built  as 
shown  in  Fig.  305.  Two  sides  are  of  I-beams  filled  in  between 
with  concrete  and  the  end  is  of  -J-inch  steel  plates.  This  form  of 
flume  is  patented,  and  the  advantage  claimed  is  that  it  takes  up 
a  minimum  of  space.  It  is  a  question  in  the  author's  mind  how 
the  expansion  of  the  heavy  steel  beams  will  affect  the  adhesion 
of  the  concrete.  Concrete  reinforced  with  wire  netting  should  be 
more  efficient  and  less  costly.  -J-inch  steel  is  apt  to  rust  out  too 
quickly  and  sweats  badly,  causing  a  damp  generator  room.  The 
space  at  A  being  of  no  value,  would  it  not  be  a  better  plan 
to  run  the  sides  straight  out  and  make  the  end  square  and  of 
reinforced  concrete  ?  Or  leave  it  round  and  make  it  of  concrete 
reinforced  with  cables  ? 

Fig.  306  shows  in  detail  the  setting  of  high  pressure  turbines. 
This  plan  is  the  latest  in  turbine  installation  for  heads  of  75  feet 
or  more,  and  is  the  product  of  the  Stillwell,  Bierce  &  Smith 
Vail  Company.  All  necessary  relief  valves  and  piping  are  here 
shown.  The  main  valves  are  operated  by  water  pressure. 

When  the  head  exceeds  about  20  to  30  feet  it  is  necessary  to 
conduct  the  water  to  the  wheels  through  penstocks.  Figs.  307 
and  308  show  the  power  house  of  the  Hannawa  Falls  Water 
Power  Company.  The  head  is  about  85  feet. 

The  plan  view  shows  an  arrangement  of  penstocks  made 
necessary  by  local  topographical  conditions  and  one  not  to  be 
recommended.  The  head  racks  have  an  area  of  200  square  feet 
and  since  each  10  foot  penstock  carries  30,000  cubic  feet  per 
minute,  the  velocity  through  the  racks,  not  allowing  for  the 


POWER  HOUSE  CONSTRUCTION. 


315 


316 


HYDROELECTRIC  PLANTS. 


space  taken  up  by  the  bars,  would  be  150  feet  per  minute, 
while  it  should  be  only  90.  Another  defect  is  the  shallowness 
of  the  water  under  the  draft  tube,  it  being  but  five  feet.  The 
area  of  the  tail  race  is  about  500  square  feet  and  the  water 
discharged  when  all  turbines  are  in  use  is  100,000  cubic  feet 
per  minute,  giving  a  velocity  of  200  feet  per  minute.  As  the 
percentage  of  head  lost  by  this  high  velocity  is  small  it  may 


m — -^~-^~-~ "_r-_^_n4^±^r- 

-  -CONCRETE- =~t_    ^ •- 


FIG.  305.— Details  of  the  "  Soo  "  plant. 

be  considered  a  good  design.  The  penstocks  are  of  5/16-inch 
and  f-inch  mild  steel,  containing  less  than  .06  per  cent,  of  phos- 
phorous. The  turbines  are  special,  having  gun  metal  bronze 
runners  of  the  Samson  type.  The  gates  are  of  cast  steel,  the 
case  and  draft- tubes  .of  rolled  steel  and  the  remainder  of  cast 
iron.  The  upper  part  of  the  building  is  for  manufacturing 
purposes. 

Fig.  309  shows  a  well  designed  plant  built  for  the  largest 
paper  mill  in  the  world  at  Millinocket,  Me.  The  part  of  the 
plant  here  shown  is  for  the  generation  of  3000  kw.  in  three  units. 
Three  pairs  of  36-inch  turbines  of  1500  h.p.  each,  drive  three 


POWER  HOUSE  CONSTRUCTION. 


317 


318 


HYDROELECTRIC  PLANTS. 


CBOSS-SECTION  OF  TUB  POWBB  HOUSE. 

FIG.  307.— Power-house. 


O 


FIG.  308.— Power-house. 


POWER  HOUSE  CONSTRUCTION. 


319 


1000  kw.  generators.  Allowing  for  80  per  cent,  efficiency  in  the 
turbines,  26,000  cubic  feet  of  water  are  required  per  minute  and 
for  the  exciters  1440,  making  27,440  cubic  feet  per  minute  in 
all.  This  gives  a  velocity  of  five  feet  per  second  in  the  11-foot 
penstock. 

It  will  be  noted  that  1125  kw.  turbines  are  used  to  drive  1000 
kw.   generators.     This  is  evidently  much  too  small  as   10  per 


FIG.  309. — Power-house. 


cent,  of  the  turbine  power  is  required 'for  regulation  and  all 
generators  should  take  a  50  per  cent,  overload  for  one  half  hour 
without  overheating,  therefore  the  full  peak  load  capacity  of 
these  generators  can  never  be  used  and  fully  20.  per  cent,  of  the 
money  invested  in  them  is  bringing  no  return.  Each  pair  of 
turbines  should  be  of  1400  kw.  capacity,  because  most  turbines 
are  most  efficient  on  J  gate,  the  turbines  depreciate  in  efficiency 


320 


HYDROELECTRIC  PLANTS. 


ffiODODQQQQ 

OQQQi 


FIG.  310.— Power-house. 


POWER  HOUSE  CONSTRUCTION. 


321 


much  more  rapidly  than  do  the  generators  with  the  result  that 
in  five  or  ten  years  the  turbine  power  will  become  too  weak 
for  the  maintenance  of  the  proper  voltage  in  the  generators. 

An  interesting  feature  of  this  plant  is  the  manner  of  bringing 
in  the  penstock  under  the  turbine. 

Fig.  310  shows  common  type  of  power  house  for  medium  heads. 
In  this  case  the  head  is  about  40  feet.  The  steel  penstocks  are 


FIG.  311. — Foreign  design  for  hydroelectric  power-house. 

brought  into  the  power  house  through  a  masonry  wall.  A 
second  wall  separates  the  turbine  cases  from  the  generator 
room,  thus  insuring  a  dry  generator  room.  The  power  house 
was  on  a  soft  bottom  and  rests  on  a  heavy  timber  mat,  no  piling 
being  driven  to  sustain  it.  This  plant  is  at  Red  Bridge,  Mass. 
To  give  the  reader  some  idea  of  foreign  practice  a  typical 
plant  is  shown  in  Figs.  311  and  312.  In  Europe  vertical  direct 


322 


HYDROELECTRIC  PLANTS. 


POWER  HOUSE  CONSTRUCTION. 


323 


324 


HYDROELECTRIC  PLANTS. 


POWER  HOUSE  CONSTRUCTION. 


325 


326 


HYDROELECTRIC  PLANTS. 


connected  generators  are  quite  common.  This  plant  works 
under  an  85-foot  head  and  develops  over  2000  h.p.  Three  of 
the  generators  are  500  h.p.  driven  by  turbines  of  650  h.p.  In 
this  case  partial  allowance  has  been  made  for  regulation  and 
the  peak  load  of  the  generator  so  that  the  full  efficiency  of  the 
generators  can  be  obtained.  Under  test  the  turbines  gave  81 
per  cent,  efficiency,  at  f  load  and  79  per  rent,  at  full  load. 
Therefore,  when  developing  487  h.p.  the  turbines  are  the  most 
efficient.  When  the  highest  efficiency  is  desired,  even  in  this 
case,  the  turbine  capacity  is  too  small,  as  at  f  load  it  should 
drive  the  generator  under  a  50  per  cent,  overload  and  the 


Transverse    .  Sec-tier 

FIG.  316. — Power-house  for  high  heads. 

governors.  However,  the  above  is  better  than  the  average 
American  practice.  Governors  made  by  Escher,  Wyse  &  Co. 
(Allis-Chalmers  Co.  are  the  American  manufacturers)  are  used, 
these  being  a  standard  make  in  Europe,  and  are  becoming 
better  known  in  America. 

Figs.  313  and  314  illustrate  the  power  plant  now  being  built 
for  the  utilization  of  the  waters  of  the  Chicago  drainage  canal. 
It  would  be  difficult,  indeed,  to  criticize  the  design  of  this  plant, 
except  that  more  reinforcing  might  have  been  used  in  the  con- 
crete, but  on  the  whole  this  plant  marks  a  distinct  advance 
in  such  construction. 

Figs.  315  to  317  give  a  good  idea  of  a  pelton  water  wheel 
plant  built  for  the  Pike's  Peak  Power  Company.  The  effective 
head  is  1160  feet.  Each  of  the  four  peltons  driving  the  gen- 


POWER  HOUSE  CONSTRUCTION. 


327 


f 
I 


t 

t^ 

.-i 
co 

I 


328 


HYDROELECTRIC  PLANTS. 


FIG.  318. — Power-house  at  Niagara  Falls. 


POWER  HOUSE  CONSTRUCTION.  329 

erators  is  of  610  h.p.,  though  by  using  one  of  the  two  wheels 
comprising  each  unit  and  by  using  different  sized  nozzles, 
almost  any  power  can  be  obtained  at  full  efficiency.  Each 
pelton  unit  drives  a  500  h.p.  generator  at  450  r.p.m.  This  plant 
was  tested  and  the  efficiency  from  water  to  switchboard  was 
78  per  cent.  All  piping  was  tested  to  800  pounds  pressure  per 
square  inch. 

Fig.  318  shows  a  5000  h.p.  unit  in  the  most  noted  hydro- 
electric plant  in  the  world,  namely,  the  Niagara  plant.  The 
turbines  were  designed  by  Escher,  Wyse  &  Company  of  Zurich, 


FIG.  319. — Example  of  power-house  architecture. 

Switzerland,  and  built  by  I.  P.  Morris  Co.,  of  Philadelphia. 
The  governors  were  the  design  of  the  same  Swiss  company, 
and  were  built  by  A.  Falkinan  of  Philadelphia.  These  governors 
permit  a  speed  variation  of  five  per  cent,  from  full  to  no  load, 
and  for  ordinary  load  variation  is  as  good  as  modern  steam 
engine  practice.  The  generators  are  of  the  two-phase  type. 
Much  of  the  power  is  used  by  electric  furnaces  using  single 
phase  current.  This  unbalances  the  generator  load  and  taxes 
the  regulation  to  the  utmost.  The  regulation  of  voltage  is 
within  ten  per  cent. ;  the  efficiency  of  the  generators  is  98  per 
cent.;  the  working  head  on  the  turbines  is  161  feet. 


330 


HYDROELECTRIC  PLANTS. 


ARCHITECTURE. 

It  costs  but  very  little  more  to  give  to  the  exterior  of  a  power 
house  or  head  works  a  fine  appearance,  and  in  after  years  the 
appearance  may  be  an  important  factor  in  the  price  for  which 
the  property  will  sell. 


FIG.  320. — Architecture  suitable  for  head-gates,  arches,  etc. 

Figs.  319  and  320  show  some  types  of  construction  which 
have  been  used  on  numerous  well-know  structures,  and  may 
aid  the  engineer  in  the  design  of  hydroelectric  power  plants. 


CHAPTER  VII. 


POWER    HOUSE    EQUIPMENT. 

WATERWHEELS. 
TURBINES. 

Like  all  other  matters  pertaining  to  hydraulics,  the  turbine 
has  made  slight  progress  in  the  last  50  years.  In  1840  the 
Swain  turbine  gave  80  per  cent,  efficiency  on  test  and  the  LeiTel 
74  -per  cent.  The  following  is  a  list  of  some  of  the  most  prom- 
inent turbines.  The  efficiency  given  is  the  catalogue  value, 
and  even  an  efficiency  of  80  per  cent,  is  seldom  guaranteed. 
The  only  improvement  has  been  in  size,  and  speed  and  efficiency 
at  part  gate. 

TABLE  XXXIX. 
COMPARISON  OF  VARIOUS  MAKES  OF   WHEELS. 


Wheels. 

Diam- 
eter. 

Head. 

Revolu- 
tions. 

H.P. 

Water 
cu.  ft. 
per  mm. 

Effi- 
ciency. 

Hercules  :  .  .  .  . 

30  inches 

20  feet 

174 

119.59 

3,960 

80% 

Samson  
McCormick 

30       " 
30 

20     " 
20     " 

242 
186 

162.00 
142  70 

5,312 
4  721 

80% 
80% 

Victor  

30       " 

20     " 

210 

165.35 

5,471 

80% 

Rice's  Victor  
Hunt                      •  

30       " 
30 

20     " 
20     " 

222 

187 

183.72 
111  52 

6,079 
3  556 

80% 
80% 

30 

20     " 

107 

100  78 

3  273 

82°7n 

Most  of  the  turbine  makers  give  the  results  of  tests  performed 
at  testing  flumes,  proving  high  efficiency,  but  it  is  the  author's 
opinion  that  little  dependence  should  be  placed  on  these.  There 
is  no  question  but  that  the  tests  are  correctly  performed  but  the 
wheel  makers  do  not  give  to  the  public  all  the  data  connected 
with  the  test.  This  is  known  to  have  been  the  case  in  several 

331 


332  HYDROELECTRIC  PLANTS. 

\ 
instances.     The  only  safe  way  is  to  have  a  written  guarantee 

from  the  makers.  | 

Turbines  may  be  divided  into  three  general  classes  which  will 
serve  the  purposes  of  this  book:  Register  gate,  wicket,  and  cylinder 
gate.  All  turbines  are  now  made  in  both  the  horizontal  and 
vertical  forms.  They  all  have  a  runner  of  the  same  general  type. 
Fig.  321  shows  a  Victor  runner  and  it  typifies  many  others. 
This  is  the  part  of  the  turbine  which  revolves.  The  buckets 
are  usually  of  steel  cast  into  the  cast  iron  frame. 


FIG.  321. 

Among  the  wicket  gate  turbines  the  Leffel  and  American 
are  the  most  prominent.  The  former  has  a  greater  speed  than 
any  other,  and  in  construction  is  one  of  the  strongest. 

In  the  latest  Leffel  and  Victor  wheels  the  gates  are  operated 
by  a  ring  and  lever  (Figs.  360  and  324)  instead  of  the  numer- 
ous rods  shown  in  Figs.  322-323.  This  is  an  important  improve- 
ment where  a  sensitive  governor  is  used  as  the  number  and 
weight  of  the  moving  parts  are  greatly  reduced.  This  wheel 


POWER  HOUSE  EQUIPMENT. 


333 


can   be   used  for  heads  up  to   40  feet.     They  have  a  good  part 
load  efficiency. 

Turbines  built  by  the  S.  Morgan  Smith  Company  are  for  the 
most  part  of  the  cylinder  gate  type.  A  form  of  wicket  gate  as 
made  by  the  above-mentioned  company,  is  shown  in  Fig.  324. 
It's  mode  of  operation  is  immediately  apparent  from  the  illus- 
tration. Fig.  325  shows  a  double  turbine  built  by  the  S. 


FIG.  322. 

Morgan  Smith  Company.  This  turbine,  as  will  be  seen  from 
the  controlling  devices,  is  of  the  cylinder  gate  type.  It  was 
built  to  operate  under  a  head  of  85  feet. 

The  greater  proportion  of  turbines  are  of  the  cylinder  type. 
Fig.  326  shows  a  sectional  view  of  a  Victor  turbine  made  by  the 
Platt  Iron  Works  Company  of  Dayton,  Ohio.  This  is  their 
latest  wheel  and  the  invention  of  A.  C.  Rice ;  A  and  A '  are 
the  runners,  and  F  and  F'  the  cylinder  gates  operated  in  the 
direction  of  shaft  by  the  rods  a  and  a' .  The  gears  operating 
these  gate  rods  are  run  in  oil  and  project  through  the  bulkhead 


334 


HYDROELECTRIC  PLANTS. 


into  the  power  house.  All  cylinder  gate  turbines  have  a  gate 
similar  to  the  Victor  gate.  The  cylinder  gate  is  more  nearly 
water  tight  than  the  registering  gates,  but  taken  with  the 
counter  weight  used  to  balance  them  they  are  heavier  than  the 
register. 

The  Platt  Iron  Works  Company  makes  a  high  pressure  tur- 
bine which  can  be  used  with  heads  of  from  70  to  TOO  feet. 
They  thus  fill  in  the  gap  between  the  ordinary  turbine  and  the 


FIG.  323. 

Pelton.  In  operating  turbines  under  high  heads  it  is  imperative 
that  all  grit  be  removed  from  the  water  before  it  is  passed 
through  the  wheels,  otherwise  the  wheels  soon  wear  out.  On 
such  wheels  all  running  parts  should  be  made  of  bronze.  The 
action  of  water  under  high  pressure  is  such  that  holes  are  often 
bored  through  solid  cast  iron  by  the  impact  of  the  fluid. 

Under  heads  above  50  feet,  an  efficiency  of  75  per  cent,  is 
very  good,  and  for  the  average  gate  opening  this  is  too  high, 
for  heads  above  200  feet  80  per  cent,  is  a  fair  efficiency. 


POWER  HOUSE  EQUIPMENT. 


335 


Wheels  tested  at  Holyoke,  Mass.,  are  tested  under  the  most 
favorable  conditions.  The  wheel  is  new  and  smoothed  up  un- 
usually well.  The  setting  is  perfect,  and  all  parts  are  new  and 
water-tight. 

After  a  year  or  so  of  use  all  turbines  become  more  or  less 
leaky,  out  of  alignment  and  the  buckets  become  dented  and 
rough.  It  is  no  uncommon  thing  for  the  J-inch  steel  buckets 
to  get  knocked  partly,  out  of  the  casting. 

There  are  numerous  forms  of  turbine  settings,  a  few  of  which 


FIG.  324. 


are  given  in  Figs.   327  to  341.     Cf  course  any   slant  may  be 
given  the  various  pipes  and  draft  tubes. 

There  has  been  such  a  fad  for  horizontal  turbines  that  they 
were  often  installed  where  the  vertical  type  would  be  prefer- 
able. The  horizontal  turbine  allows  the  placing  of  two  or  more 
turbines  on  one  shaft,  thus  getting  increased  speed  with  the 
same  power  or  increased  power  with  the  same  speed.  How- 
ever, their  use  usually  necessitates  a  generator  of  slower  speed 
than  would  the  vertical  type,  and  hence  of  more  cost  and  makes 
regulation  within  wide  limits  of  head  an  impossibility.  When 


336 


HYDROELECTRIC  PLANTS. 


the  frequency  is  not  of  prime  importance,  the  ordinary  ex- 
citation of  a  generator  can  take  care  of  a  10  per  cent,  reduction 
in  speed,  but  beyond  this  the  voltage  will  fall,  therefore,  where 


*     "*'  X 


severe   reduction   in   head   is   to   be   apprehended,   the   vertical 
turbine  with  its  noisy  gearing  may  be  the  best  practice  as  with 


POWER  HOUSE  EQUIPMENT. 


337 


a  proper  ratio  of  gearing  and  a  sufficient  number  of  turbines 
the  speed  of  the  line  shaft  can  be  kept  up. 

The  determining  factors  as  to  the  selection  of  the  horizontal 
turbine  should  be:  One,  the  speed  variation  under  all  probable 
stages  of  head  and  back  water;  two,  additional  cost  of  ma- 
chinery, due  allowance  being  made  for  the  increased  efficiency 


FIG.  326. 


of  the  horizontal  wheel.  (The  same  wheel  mounted  in  a  hori- 
zontal position  would  have  an  efficiency  about  three  per  cent, 
less  than  in  the  vertical  position,  but  since  about  10  per  cent, 
or  more  is  lost  in  the  gearing,  etc.,  the  turbine  will  be  about 
seven  per  cent,  more  efficient  in  the  horizontal  position  than 
in  the  vertical;)  three,  cost  of  turbine  setting. 


338 


HYDROELECTRIC  PLANTS. 


FIGS.  327-331. 


FIGS.  332-333. 


FIGS.  334-336. 


FIGS.  337  339. 


FIGS.  340-341. — Typical  Turbine  Settings 


POWER  HOUSE  EQUIPMENT. 


339 


There  must  be  at  all  times,  from  six  feet  to  ten  feet  of  water 
at  Ay  Fig.  335,  to  prevent  air  bubbles  and  whirlpools.  Horizon- 
tal wheels  have  been  used  on  heads  as  low  as  15  feet.  The 
great  Soo  plant  has  16  feet  head  and  the  turbines  (Hunt)  gave 
84  per  cent,  efficiency  on  test 

It  sometimes  happens  that  a  water  power  is  to  be  developed 
at  a  head  considerably  below  that  to  which  it  will  be  increased 
later  on,  and  it  is  desired  to  install  generators  and  turbines 
which  will  answer  for  both  heads.  The  following  setting  was 
designed  by  Mr.  M.  E.  Powers  (Fig.  342).  The  gears  were  so 


FIG.  342. 

proportioned  that  at  the  reduced  head  the  generator  had  the 
proper  speed.  The  turbines  were  selected  so  that  under  the 
increased  head,  the  generator  shown  in  sketch  could  be  moved 
directly  over  it  and  direct  connected  to  it.  A  second  generator 
was  then  installed  and.  set  over  the  other  turbine.  The  gears 
were  therefore  all  there  was  to  be  discarded. 

Wherever  possible  it  is  best  to  place  two,  four  or  six  turbines 
on  a  shaft  so  as  to  balance  the  end  thrust  (see  Figs.  329,  332, 
335  and  339). 

An  open  setting,  Figs.  327,  335,  336  and  337,  should  be  ob- 
tained when  possible,  the  efficiency  being  greater  and  the 
governing  better. 


340  HYDROELECTRIC  PLANTS. 

Fig.  341  shows  about  the  only  alternative  where  the  varia- 
tion between  high  and  low  water  exceeds  the  maximum  prac- 
ticable length  of  draft  tube,  and  where  it  is  desired  to  maintain 
the  speed  and  power  with  direct  connected  units.  The  back 
water  wheel  No.  1,  runs  idle  during  normal  water,  but  is  used 
when  the  back  water  reaches  the  draft  tube. 

Next  to  lack  of  water  during  the  months  of  minimum  flow, 
the  reduction  of  head  by  back  water  is  the  most  serious  osbtacle 
the  hydraulic  engineer  has  to  contend  with.  One  good  feature, 
however,  is  that  we  have  plenty  of  water,  so  that  by  installing 
enough  turbines  and  properly  gearing  them,  we  may  keep  up 
the  speed  of  the  line  shaft  and  also  the  power. 

Ordinarily  building  the  dam  does  not  affect  the  stage  of  back 
water.  Its  cause  lies  below  the  dam,  and  is  due  to  the  choking 
effect  of  the  river  banks,  islands,  bends,  etc.  Usually  the  high 


FIG.  343. 

water  mark  can  be  distinguished  by  the  driftwood  along  the 
banks.  It  is  seldom  indeed  that  there  are  not  somewhere 
sure  indications  of  the  high  water  mark.  Farmers  along  the 
river  can  corroborate  the  evidence,  so  that  there  should  be 
no  trouble  in  determining  the  back  water  stage. 

The  depth  of  water  over  the  dam  is,  as  a  rule,  more  difficult 
to  pre-determine.  If  there  is  a  dam  anywhere  above ,  the  problem 
is  an  easy  one.  As  a  rule,  if  you  build  a  dam  in  a  river  having 
parallel  shores,  as  in  Fig.  343,  the  water  will  pile  up  below 
the  dam  twice  as  much  as  it  does  above.  If  the  dam  is  narrower 
than  the  average  width  of  the  stream,  the  difference  will  of 
course  be  less. 

Take  an  example  where  we  have  20  feet  of  head  at  normal 
stages.  Suppose  we  frequently  have  the  head  -diminished  five 
feet  due  to  back  water,  and  in  extreme  cases  our  head  is  reduced 
to  ten  feet.  Then  for  a  series  of  turbines  all  having  the  same 
p«wer  with  same  head,  we  have  the  following: 


POWER  HOUSE  EQUIPMENT.  341 

EXAMPLE: — We  wish  to  drive  a  350  h.p.  generator  at  290 
r.p.m.  and  we  do  not  want  the  speed  to  fall  below  260  as  the 
field  rheostats  of  the  generator  will  not  take  care  of  a  greater 
variation.  The  normal  flow  of  the  stream  will  just  supply  the 
one  wheel. 

Referring  to  tables  for  the  Samson  turbine  we  find  that 
a  50-inch  Samson  will  give  451  h.p.,  at  145  r.p.m.  under  a  20-foot 
head. 

First.  Under  normal  conditions  the  first  pair  of  gears  (Fig.  344) 
will  be  in  the  ratio  of  2  to  1  and  turbine  No.  2  will  be  thrown 
out  of  gear. 

Second.  The  head  becomes  reduced  to  15  feet  and  the  speed  of 
the  generator  falls  to  252  r.p.m.  Now  if  but  one  turbine  were 
in  gear  the  ratio  of  the  gears  would  be  1  to  2.3  to  keep  the  speed 
at  290,  as  under  15-foot  head  a  50-inch  Samson  has  126  r.p.m.; 


FIG.  344. 

but  the  power  would  be  too  low,  being  only  293  h.p.  We  there- 
fore gear  turbine  No.  2  in  the  ratio  of  1  to  2.6.  The  speed  of 
the  line  shaft  will  then  be  a  mean  between  the  two  sets  of  gears. 

^—1?   =  2.3  and  2.3 X  126  =  298.8.    With  the  two  turbines  we 

have  under  15-foot  head  586  h.p.  We  have  therefore  kept  up 
the  speed  and  power. 

Third.  Head  reduced  to  10  feet;  three  50-inch  Samsons  under 
10-foot  head  will  give  480  h.p.  at  103  r.p.m. 

With  turbines  No.  1  and  2  geared  as  above  the  speed  will 
be  237  r.p.m.  Now  if  we  add  a  third  turbine  we  do  not  double 
the  power  as  before,  but  have  to  allow  for  the  action  of  a  one- 
third  power  acting  on  the  two-third  power. 

We  have  the  following  formulas  for  any  number  of  turbines: 


342  HYDROELECTRIC  PLANTS. 

where  X  =  the  ratio  to  be  found;  R  =  the  number  of  revolu- 
tions desired  on  the  line  shaft.  TV  =  the  number  of  turbines 
including  the  turbine  the  ratio  of  whose  gears  it  is  desired  to 
find;  R'  =  the  revolutions  of  the  turbines  under  the  reduced 
head  (found  from  turbine  tables)  at  which  the  n'th  turbine 
is  thrown  into  gear.  .4  =  the  ratio  of  the  gears  of  turbine  No.  1. 
B  =  ratio  of  gears  of  turbine  No.  2.  C  would  =  ratio  of  No.  3, 
etc. 


Thus  in  the  above  example,  X  =  -     -  (2  +  2.6)  ;  X   « 


3.846.     If  we  add  another  turbine  for  a  head  of  only  eight  feet 
we  find  that  all  the  turbines  will  have  a  velocity  of  92  r.p.m. 

9QO  v4 

and  X  =  ——^--(2  +  2.6  +  3.73)  =4.27   as   the   ratio   of   the 

fourth  set  of  gears.     The  power  is  456  h.p. 

Care  must  be  taken  in  keeping  the  proper  proportions  for  the 
gears;  that  is,  the  speed  of  the  teeth,  pressure,  etc. 

It  is  this  ability  to  regulate  the  speed  and  keep  up  the  power 
that  often  makes  it  desirable  to  install  vertical  rather  than 
horizontal  turbines.  Of  course,  the  head  works  must  be  given 
sufficient  area  to  take  care  of  the  great  quantity  of  water  used 
under  the  reduced  head. 

During  periods  of  flood,  a  velocity  of  100  feet  may  be  used 
through  the  racks  and  200  feet  through  the  tail  race  as  efficiency 
is  not  so  important  at  high  water  as  are  speed  and  power. 

Since  every  turbine  has  a  certain  velocity  at  which  it  is  most 
efficient  the  above  arrangement  will  not  be  of  high  efficiency, 
but  at  the  time  the  extra  turbines  are  thrown  into  gear  there 
is  plenty  of  water.  The  lower  geared  turbines  are  made  to  race 
while  the  higher  gears  cause  the  turbines  to  work  at  a  low  speed. 
Under  extreme  conditions  of  back  water  the  low  geared  wheels 
may  develop  no  power  at  all  in  which  case  they  would  be  cut  out.. 

By  the  use  of  the  draft  tube  any  turbine  may  be  placed 
above  tail  water.  This  distance  B,  Figs.  327  and  336,  is  theo- 
retically 34  feet,  but  in  practice  there  are  reasons  why  the 
length  should  be  about  as  given  in  the  table  by  Mr.  John  Wolf 
Thurso. 


POWER  HOUSE  EQUIPMENT.  343 

Diameter  of 

draft  tube 

in  feet.        =    0.5     1        23        4567        8     9   10  11       12   13    14 
Draft  head 

in  feet.       =32.5  30  27.5  25  22.5  20  18  16  14.5  13  12  11   10.5  10  9.5 

By  draft  head  is  meant  the  vertical  distance  between  the 
center  of  shaft  and  the  tail  water  for  horizontal  wheels  and 
between  the  center  of  the  guide  buckets  for  vertical  turbines, 
as  B  in  Fig.  327. 

This  table  gives  draft  heads  slightly  too  small  for  turbines 
under  steady  loads  and  working  at  full  gate  and  too  great  a 
head  for  rapidly  fluctuating  loads  and  partial  gate. 

Draft  tubes  should  always  be  conical.  The  proper  diameter 
for  any  particular  draft  tube  may  be  figured,  using  the  above 
table  as  follows:  A  conical  draft  tube  must  not  be  more  than 

/  V2  \ 

12  feet  in  diameter,  at  a  height  of  (10-5  — ^— ;)  feet  above  tail 

water,  where  V  =  .285  \/64.4  H. 

Short  and  small  tubes  must  dip  into  the  tail  water  6  in- 
ches to  12  inches  and  20  inches  to  24  inches  for  long  and  large 
tubes.  A  greater  dip  permits  a  greater  draft  head  within  limits. 

Where  heads  fluctuate  badly  and  a  sensitive  governor  is  used, 
the  wheels  should  set  close  to  tail  water  to  avoid  oscillations. 

Even  where  the  turbine  sets  below  tail  water  a  draft  tube 
increases  the  efficiency. 

Frequently  with  large  draft  tubes  when  running  at  part 
gate  the  draft  tube  does  not  fill  with  water  at  all,  and  the 
turbine  runs  under  a  severe  loss  of  head.  Draft  tubes  are  gen- 
erally made  much  too  thin,  3/1.6  inch  is  a  common  thickness, 
while  good  practice  would  be  nothing  thinner  than  J-inch.  The 
velocity  of  the  water  amounting  to  about  twice  the  peripheral 
speed  may  be  calculated  from  V  =  .285  \/64.4  H,  where  V  is 
velocity  in  feet  per  second  and  H  is  the  total  head  acting  on 
turbines  in  feet. 

All  turbine  settings  should  be  provided  with  a  gauge,  A, 
Fig.  345,  to  indicate  the  pressure  at  turbine  due  to  the  head, 
and  a  vacuum  gauge  B  to  indicate  the  vacuum  in  the  draft 
tube  due  to  the  draft  head. 

Throttling  gates  should  never  be  used  to  regulate  the  speed, 
on  account  of  the  great  waste  of  power. 


344 


HYDROELECTRIC  PLANTS. 


All  turbine  makers  supply  books  giving  dimensions  of  flumes 
for  different  sized  wheels  and  tables  of  speed,  power  and  quan- 
tity of  water  for  different  sized  turbines  under  various  heads. 


FIG.  345. 

Whether  the  turbine  chamber  is  of  wood,  masonry  or  steel, 
the  water  should  be  admitted  to  the  wheel  and  conducted  away 
from  it  at  a  velocity  of  about  80  feet  to  90  feet  per  minute. 


FIG.  346. — Setting  for  cylinder  gate  turbine. 

Of  course,  if  to  gain  this  condition  necessitates  an  expenditure 
of  more  than  the  head  gained  is  worth,  a  higher  velocity  is  ad- 
visable. By  referring  to  the  tables  giving  the  water  used  by 


POWER  HOUSE  EQUIPMENT. 


345 


the  selected  wheels  and  dividing  this  quantity  of  water  by 
80  or  90,  the  proper  area  of  the  wheel  chamber,  that  is  A  H 
(Fig.  346)  is  obtained.  The  area  C  D  should  also  equal  A  H 
where  practicable,  though  often  the  added  cost  of  a  deep  wheel 
pit  will  not  warrant  a  lower  velocity  than  100  feet  per  minute. 

The  effective  depth  of  tail  water  should  be  take.n  as  D  —  E. 
Where  the  desired  depth  is  not  attainable,  a  diffuser  K,  or  a 
concrete  diffuser  should  be  used. 

The  tail  race  is  not  usually  continued  down  stream  at  the 
depth  D,  but  is  gradually  shallowed  and  widened  so  that  the 


FIG.  347. 

area  A' Er  =  A  B,  Fig.  347,  the  race  discharging  into  the 
river  on  an  angle. 

As  the  speed  of  a  turbine  grows  less  with  the  increase  in  size? 
two  or  more  small  turbines  may  be  mounted  on  the  same  hori- 
zontal shaft.  There  is  a  further  advantage  in  having  several 
small  wheels  rather  than  one  large  one,  in  that  there  is  less 
trouble  with  the  draft  tubes. 

The  floor  upon  which  the  turbine  rests  must  be  perfectly 
unyielding.  It  supports  not  only  the  water  but  also  the  tur- 
bine. Whenever  the  depth  of  water  over  turbines  will  permit, 
set  the  wheels  high  enough  above  tail  water  so  that  a  man 
can  pass  under  the  floor  of  the  flume,  and  by  removing  a  man-hole 


346 


HYDROELECTRIC  PLANTS. 


cover  provided  for  the  purpose  in  the  draft  tube,  adjust  the 
step  of  the  turbine  (Fig.  348).     Some  form  of  step  adjustment 


FIG.  348. 


1T 


FIG.  350. 


other  than  that  usually    used    should    be   designed.     Figs.  349 
and  350  are  given  as  suggestions. 


POWER  HOUSE  EQUIPMENT.  347 

THE   PELTON   WHEEL. 

Pelton  is  the  name  commonly  given  to  that  form  of  water 
wheel  which  receives  its  water  power  from  the  force  of  one  or 
more  jets  of  water  directed  against  the  numerous  cup-like 
vanes  situated  around  its  periphery.  This  wheel  is  also  called 
the  hurdy-gurdy  wheel,  or  tangential  wheel. 

Fig.  351  shows  a  Pelton  mounted  in  an  iron  frame.  The 
water  after  leaving  the  vanes  drops  down  to  tail  water  utilizing 
none  of  the  fall  from  the  bucket  down.  Thus  on  a  low  head, 
especially  when  there  is  liability  of  back  water,  a  serious  pro- 
portion of  the  head  is  lost. 


FIG.  351.  —Pelton  water  wheel. 

As  now  constructed,  the  Pelton  uses  a  nozzle  so  small  that 
the  power  derived  from  it  is  quite  insignificant  comparatively. 
To  increase  the  power  of  the  Pelton,  the  velocity  being  fixed 
by  the  machinery  they  are  to  drive,  two  expedients  are  resorted 
to. 

One.  The  diameter  of  the  wheel  may  be  increased  to  as  great 
a  diameter  as  required  to  give  the  power.  33  feet  is  the  greatest 
diameter  in  use;  12  feet  is  rather  uncommon,  and  six  feet  is 
the  largest  standard  size. 

Two.  The  number  of  nozzles  may  be  increased.  The  Pelton 
Water  Wheel  Company  built  a  quintex  Pelton  or  a  five-nozzle 


348  HYDROELECTRIC  PLANTS. 

wheel.  Again  for  any  large  units  more  than  one  wheel  may  be 
mounted  on  the  same  shaft.  Of  course,  all  this  complicates 
the  plant  and  there  comes  a  time  when  the  complication  makes 
the  high  pressure  turbine  preferable  to  the  Pelton.  For  heads 
up  to  about  150  feet  and  for  powers  of  over  500  h.p.  the  turbine 
has  as  great  an  efficiency,  is  cheaper,  and  is  preferable  to  the 
Pelton.  For  higher  heads  up  to  300  feet  and  large  powers 
the  field  is  open  to  both  the  Pelton  and  the  turbine,  but  above 
this  head  the  Pelton  begins  to  rapidly  out-distance  the  turbine 
in  point  of  cost  and  efficiency.  There  are  quite  a  number  of 
plants  in  operation  where  a  head  of  from  1200  to  1GOO  feet  is 
utilized  successfully. 

Tables  giving  the  sizes  and  powers  of  the  standard  Pelton  may 
be  obtained  from  the  manufacturer.  In  these  tables  the  "  ef- 
fective "  head  is  given,  that  is,  the  vertical  distance  between 
surface  of  the  head  water  and  the  point  where  the  water  strikes 
the  vanes,  and  not  the  distance  down  to  tail  water  as  for  the 
turbine. 

As  will  be  seen  from  Fig.  351  the  weights  of  the  revolving 
parts  are  quite  light  and  therefore  add  very  little  to  the  regula- 
tion of  speed  under  a  fluctuating  load.  It  is  therefore  quite 
necessary  to  use  a  heavy  fly  wheel  where  good  government  is 
essential.  In  many  large  plants  the  weight  of  the  generator- 
armatures  or  fields  is  depended  on.  Where  the  generator  is 
of  the  revolving  field  type  this  may  be  sufficient. 

For  high  efficiency  the  velocity  of  the  water  issuing  from  the 
nozzle  must  remain  at  a  maximum.  The  Pelton  Water  Wheel 
Company  regulate  their  wheels  in  four  different  ways. 

(1)  By  deflecting  the  nozzle  so  that  the  water  does  not  hit 
the  vanes. 

(2)  A  cut-off  hood  is  placed  in  front  of  the  nozzles  by  means 
of  which  the  discharge  area  of  the  nozzle  is  varied. 

(3)  A  deflecting  plate  is  used  to  deflect  the  water. 

(4)  A  plug  nozzle  is  used.     In  this  nozzle  a  tapering  pin  or 
needle  is  placed  like  the  valve  of  a  steam,  water  injector,  the 
operation  of  which  regulates  the  quantity  of  discharge  without 
materially  affecting  the  velocity.     The  Doble  needle  regulating 
nozzle  (Fig.  366)  is  the  best  on  the  market.      It    is   made    by 
Abner  Doble  Co.,  San  Francisco,  Cal. 

Any  form  of  water  wheel  governor  may  be  used  with  the  Pelton, 
either  to  deflect  the  nozzle  or  to  alter  the  area  of  discharge. 


POWER  HOUSE  EQUIPMENT.  349 

An  excellent  plan  where  for  certain  periods  the  power  is  greatly 
reduced  is  to  have  several  nozzles,  any  one  of  which  may  be  shut 
off  by  hand,  leaving,  say,  one  nozzle  to  carry  the  reduced  load 
This  gives  the  maximum  efficiency. 

REGULATION. 

Long  pipes  carrying  water  for  power  purposes  are  subject 
to  great  abnormal  pressures  due  to  the  quick  shutting  off  of 
the  water  from  the  turbines. 

The  water  under  motion  has  acquired  a  certain  amount  of  mo- 
mentum which  is  proportional  to  the  product  of  the  weight  and 
velocity.  To  arrest  this  momentum  requires  power  or  some 
means  must  be  provided  for  the  escape  of  the  energy.  In  the 
early  history  of  the  development  of  water  powers  under  high 
heads,  some  of  our  best  engineers  met  with  serious  accidents 
such  as  the  bursting  of  huge  steel  pipes  and  the  flooding  of 
power  houses;  but  now  that  the  agents  of  destruction  are  known, 
provision  is  made  for  their  subjection. 

To  secure  the  best  regulation,  what  is  known  as  an  open 
setting  should  be  approached  as  nearly  as  the  conditions  will 
permit.  That  is,  the  conditions  secured  in  the  design  for.  the 
power  house  at  Nobelsville,  Ind.  (see  Figs.  352  and  353),  where 
the  water  stands  directly  over  the  turbines  with  no  appreciable 
loss  of  head  at  any  point.  The  Yorktown  plant  (Fig.  300)  is  also 
an  example.  Where  a  long  penstock  is  used,  this  condition  may 
be  approximated  by  providing  a  small  reservoir  at  the  outlet 
of  the  penstock.  The  size  of  this  reservoir  will  depend  on  the 
sensitiveness  of  the  governor,  and  should  equal  the  amount  of 
water  the  penstock  will  carry  in  twice  the  time  necessary  to 
close  the  turbine  gates.  If  the  gate  is  left  closed  the  reservoir 
will  run  over  unless  its  level  is  above  the  inlet  of  the  penstock 
and  its  capacity  about  equal  to  that  of  the  entire  penstock. 
Usually  a  standpipe  made  of  steel,  see  Fig.  354,  of  only  a 
few  feet  diameter  is  used,  in  which  case  the  water  immedi- 
ately runs  out  at  the  top,  when  the  gates  are  quickly  shut.  This 
relieves  the  pressure  on  the  pipe  line  and  the  water  stored  in 
the  pipe  under  the  increased  head  supplies  the  succeeding 
demand  for  power  while  the  water  is  getting  up  to  speed  again. 

The  overflow  of  the  standpipe  should  be  on  a  level  with  the 
surface  of  high  water  at  the  inlet  of  penstock,  unless  the  fall 


350 


HYDROELECTRIC  PLANTS. 


L..J 


POWER  HOUSE  EQUIPMENT. 


351 


352 


HYDROELECTRIC  PLANTS. 


in  the  line  is  so  great  that  the  pressure  on  the  penstock  (head  H, 
Fig.  354),  would  be  excessive  when  the  standpipe  is  filled. 
In  this  case  the  standpipe  would  give  place  to  safety  valves 
along  the  line  of  penstock.  Standpipes  must  be  protected 
from  freezing.  In  Fig.  355,  c  is  a  standpipe  with  a  tank  at  the 
upper  end  and  large  enough  to  take  care  of  the  fluctuating  water. 


FIG.  354. 

Safety  valves  similar  to  those  on  a  steam  boiler  are  built.  They 
should  be  able  to  discharge,  when  open,  the  full  flow  of  the 
penstock. 

Fig.  355  indicates  the  location  of  the  safety  valve  at  a.  This 
should  be  so  placed  that  the  overflowing  water  will  escape 
into  the  tail  race.  Where  there  is  a  high  place  in  the 


FIG.  355. 


penstock  air  valves  must  be  placed  as  at  b,  to  prevent 
the  formation  of  air  plugs,  or,  where  the  height  is  not  too  great, 
a  better  plan  is  to  place  standpipes  at  these  points.  Galvanized 
sheet  iron  will  often  serve  the  purpose  as  at  6'. 

The  ordinary  steel  standpipe  such  as  is  used  by  city  water  works 
and  here  shown  at  c,  Fig.  355,  makes  an  excellent  standpipe. 
It  must  be  heated  in  winter  to  prevent  freezing. 


POWER  HOUSE  EQUIPMENT. 


353 


Fig.  356  shows  a  good  design   for  a  concrete-steel  stand  pipe. 

Figs.  357  and  358  show  two  types  of  cheap  governor  made 
by  the  Woodward  Governor  Company.  These  are  considered 
by  the  author  to  be  the  best  cheap  governors  on  the  market. 


FIG.  356. 

Governors. 

The  selection  of  governors  should  first  be  made  after  a  thor- 
ough study  of  the  situation.  Sensitive  governing  means  severe 
wear  and  tear  on  the  gates,  and  should  be  avoided  where  pos- 


354 


HYDROELECTRIC  PLANTS. 


o 

tuO 

1 


POWER  HOUSE  EQUIPMENT. 


355 


sible.  Many  lighting  plants  are  successfully  operated  where  it 
requires  20  seconds  to  close  the  gates  and  while  20  seconds 
may  be  the  extreme,  it  has  been  the  author's  experience  that 
for  all  but  the  most  important,  or  special  plants,  5  seconds 
is  quite  satisfactory. 

The  approximate  energy  necessary  to  operate  turbine  gates, 
which  are  properly  balanced  and  installed,  is  given  in  Table 
XL.  Where  it  is  desired  to  obtain  the  energy  necessary  to  op- 
erate gates  which  are  already  installed,  the  test  can  be  made 


DIMENSIONS,  SIZE  B.     HORIZONTAL  MODEL 

Compensating  Type  Governor 

ALL  shafts  may  revolve  in  either  direction 
desired. 

NOTE  optional  positions  for  Speed  Governor 
Pulley. 

MAIN  SHAFT  may  be  extended  on  either 
end  of  governor  to  take  Main  Pulley. 

BACK  SHAFT  nay  extend  on  either  or  both 
ends  to  connect  to  gate. 


FIG.  358. — Horizontal  Woodward  governor. 

by  turning  a  hand  wheel  of  known  radius  through  the  medium 
of  a  spring  balance.  The  test  should  include  a  measurement 
of  the  pounds  necessary  to  start  the  gate;  to  move  it  when 
0.25  open;  to  move  it  when  0.5  open,  and  to  move  it  when  0.75 
open.  From  these  measurements  the  average  foot  pounds  is 
found  by  multiplying  average  pull  in  pounds  by  the  product 
of  the  circumference,  in  feet,  of  the  hand-wheel  and  the  num- 
ber of  turns  necessary  to  close  the  gate. 

A  powerful  governor  is  one  which  will  in  a  given  number  of 


356 


HYDROELECTRIC  PLANTS. 


seconds  from  rest  bring  up  to  a  high  velocity  a  mass  of  iron 
sometimes  weighing  several  thousand  pounds.  Every  moving 
part  connected  to  the  gates  must  be  set  in  motion  regardless  of 
friction. 

In  the  case  of  cylinder  gate  turbines  the  cylinder  c  is  counter- 


FIG.  359. 

balanced  by  means  of  a  weight  W  (Fig.  359).  The  governor 
must  therefore  move  the  weight  and  cylinder  as  well  as  the 
gears,  shafts,  etc. 

The  turbine  having  wicket  gates  as  in  Fig.  324  is  balanced 
by  water  pressure  so  does  not  require  a  counter-balance.     There 


FIG.  360. 

are  more  parts  to  get  out  of  order  than  with  a  cylinder  gate, 
but  the  regulation  may  be  more  perfect  and  requires  a  less 
powerful  governor. 

In  Fig.  359  the  governor  operates  the  gate  stem  5  only, 
which  may  be  reciprocated  or  revolved  to  suit  the  conditions. 

Fig.  360  shows  a  plan  view  of  a  wicket  gate  turbine.     Until 


POWER  HOUSE  EQUIPMENT. 


357 


recently  the  collar  C  was  operated  by  gear  wheels  and  a  rod 
running  to  each  gate,  but  in  the  present  form  of  Leffel  and 
Smith  turbines  the  parts  are  reduced  in  number  and  also  the 
weight.  The  governor  works  the  draw  bar  R  to  cause  the 
rotation  of  the  collar  C. 

All  bearings  for  the  various  parts  of  turbine  gates  should  be 
of  bronze  and  of  liberal  proportions. 


TABLE  XL. 
FOOT  POUNDS  REQUIRED  TO  OPERATE  TURBINE  GATES. 


H.P. 
of 

Turbine 

Head  of  Water. 

10 

15 

20 

25 

30 

35 

40 

50 

60 

80 

100 

25 

400 

360 

330 

310 

290 

265 

250 

220 

50 

700 

630 

580 

540 

500 

470 

440 

390 

350 

310 

75 

1000 

900 

830 

770 

720 

660 

625 

550 

500 

440 

400 

100 

1200 

1080 

1000 

935 

860 

800 

750 

665 

600 

530 

465 

150 

1600 

1450 

1320 

1240 

1150 

1060 

1000 

880 

800 

700 

640 

200 

2000 

1800 

1660 

1550 

1440 

1330 

1250 

1110 

1000 

880 

800 

250 

2400 

2170 

2000 

1870 

1730 

1600 

1500 

1330 

1200 

1060 

930 

300 

2800 

2530 

2330 

2180 

2000 

1870 

1750 

1550 

1400 

1240 

1100 

400 

3600 

3250 

3000 

2800 

2600 

2400 

2250 

2000 

1800 

1600 

1400 

600 

3900 

3600 

3360 

3120 

2880 

2700 

2400 

2160 

1920 

1680 

GOO 

4500 

4200 

3920 

3640 

3360 

3150 

2800 

2520 

2240 

1960 

800 

5800 

5400 

5000 

4650 

4300 

4000 

3600 

3240 

2880 

2500 

1000 

6000 

5580 

5160 

4800 

4500 

3900 

3450 

3000 

Location  of  the  plant  should  influence  the  selection  of  a  gov- 
ernor and  where  the  plant  is  in  some  isolated  place,  the  less 
complicated  the  governor,  the  better.  Of  course  extra  parts 
could  be  kept  always  on  hand  where  the  item  of  expense  is 
second  in  importance  to  good  design.  Again  if  the  super- 
intendence of  the  plant  is  to  be  given  to  incompetent  men  (a 
common  and  costly  experiment)  the  less  complicated  the  gov- 
ernor the  better.  Throttling  valves  should  never  be  used  to 
regulated  turbines. 

Fig.  361  shows  a  standpipe  with  a  damping  pipe  a.  The 
object  of  this  pipe  is  to  prevent  the  water  oscillating  in  the 
standpipe  under  the  action  of  the  governor.  The  one  shown 


358  HYDROELECTRIC  PLANTS. 

is  three  feet  in  diameter  and  connects  to  the  standpipe  one  foot 
above  the  surface  of  the  water  in  the  distant  reservoir.  For 
heads  above  100  feet  or  so  the  standpipe  loses  part  of  its  effi- 
ciency on  account  of  the  inertia  of  the  mass  of  water  it  contains. 
The  cost  also  becomes  prohibitive  and  recourse  is  had  to  safety 
valves  and  heavy  fly-wheels.  In  fact,  all  turbines,  where  good 
regulation  is  desired,  should  be  provided  with  them. 

These  fly-wheels  range  in  weight  from  5000  pounds  to  almost 
any  weight,  and  peripheral  speeds  of  from  5000  to  10,000  feet 
per  minute,  and  are  made  of  built-up  plates,  or  cast  steel  with 
steel  tires  shrunk  on.  Fly-wheels  serve  to  take  care  of  all  the 


FIG.  361. — Stand  pipe  with  dampening  pipe. 

smaller  and  more  rapid  fluctuations  due  to  surging  in  the  pen- 
stock, draft  tubes  or  changes  of  load.  The  governor  does  not 
have  to  act  so  quickly  and  the  pressures  on  the  penstock  are 
more  easily  controlled  and  are  not  so  severe.  Vibrations  of 
the  foundation  are  minimized  and  most  of  the  noise  eliminated. 

For  fluctuating  loads  the  draft  tubes  should  be  short,  as  severe 
oscillations  are  set  up  in  long  tubes  tending  to  cause  vibrations, 
uneven  power  and  even  to  damage  the  turbine. 

The  best  governors  on  the  market  are  the  Lombard,  the  Im- 
proved Sturgess,  the  Woodward  and  the  Replogle.  The  first-three 
makes,  which  use  energy  stored  in  tanks  to  operate  the  gates, 
are  called  hydraulic  gjvernors,  while  the  Woodward  and  Re- 


POWER  HOUSE  EQUIPMENT.  359 

plogle  which  operate  the  gates  by  friction  derived  from  inertia 
balls  similar  to  those  on  a  steam  engine  governor,  are  called 
mechanical  governors. 

All  governors  are  set  into  operation  by  the  change  of  speed 
in  the  line  shaft.  A  pulley  on  the  line  shaft  drives  the  friction 
cones,  and  a  second  pulley  drives  the  governor  balls.  A  change 
of  speed  then  varies  the  position  of  the  balls  which  causes  the 
friction  cones  on  the  gate  shaft  to  operate,  or  causes  the  hy- 
draulic piston  to  act  on  the  friction  cones.  It  will  thus  be  seen 
that  the  speed  has  to  change  perceptibly  in  order  to  actuate  the 
governor,  a  fact  which  of  itself  makes  perfect  government 
impossible. 

It  would  seem  to  the  writer  that  the  first  word  "  go  "  should 
come  from  the  switchboard  rather  than  from  the  line  shaft. 
It  is  the  fluctuation  in  the  power  that  brings  about  the  change 
of  speed  which  we  wish  to  avoid.  Therefore  if  a  special 
ammeter  sets  the  governor  in  motion  a  full  second  will  be  clipped 
off  of  the  time  taken  by  the  best  governors  in  starting  the  gates. 
The  inherent  difficulty  in  attaining  perfection  in  water  power 
government  is  the  impossibility  of  setting  in  motion  the  dead 
water  in  the  pipe  or  flume  the  instant  the  gate  is  opened. 

However,  if  the  ammeter  is  used  to  start  the  governor,  all 
well-designed  water  powers  may  be  made  to  regulate  with  a 
variation  in  speed  of  less  than  three  per  cent,  on  throwing  off 
75  per  cent,  of  the  full  load,  or  two  per  cent,  under  changes 
amounting  to  50  per  cent,  full  load.  There  is  a  limit  to  the 
speed  with  which  a  gate  can  be  closed,  due  to  mechanical  rea- 
sons, 1  to  1£  seconds  is  about  this  limit.  Therefore  when  a 
second  is  lost  in  getting  the  initial  impulse  to  the  governor  it 
is  a  serious  loss. 

The  curves,  Fig.  362,  show  the  action  of  a  governor  when 
the  load  is  suddenly  increased  from  25  kw.  to  75  kw.  These 
curves  are  taken  from  Mr.  M.  A.  Replogle's  paper  read  before 
the  American  Society  of  Mechanical  Engineers,  May,  1906. 

Mr.  John  Sturgess  gives  a  set  of  curves  which  are  exactly 
like  Mr.  Replogle's  in  showing  that  valuable  time  is  lost  in  start- 
ing the  governor.  In  these  curves  it  will  be  seen  that  the 
speed  does  not  increase  perceptibly  for  fully  0.25  second.  This 
is  due  to  the  inertia  of  the  moving  machinery  and  shows  the 
importance  of  providing  a  fly-wheel  effect  where  possible.  It 


360 


HYDROELECTRIC  PLANTS. 


also  shows  that  this  effect  retards  the  action  of  the  governor 
at  the  start,  though  it  helps  it  in  the  end.  Hence  with  a  gov- 
ernor started  from  the  ammeter  we  will  have  the  governor 
acting  0.25  second  to  0.5  second  before  the  speed  varies  at  all 
and  in  another  second  the  gates  will  be  wide  open  and,  if  a 
proper  fly-wheel  is  provided,  the  regulation  will  be  practically 
perfect. 

All  governor  experts  are  agreed  that  the  cylinder  gate  turbine, 
especially  those  with   the  lip,  6,  Fig.  363,  are  the  most  difficult 


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FIG.  362. — Curves  showing  action  of  governor. 

to  govern.  There  is  a  general  tendency  now  to  build  wicket 
gate  turbines.  In  Fig.  364,  c  is  a  slide  for  the  cylinder  gate 
when  the  turbine  is  of  the  horizontal  type.  Without  this  the 
gate  is  apt  to  bind.  Another  defect  in  the  cylinder  gate  is  its 
poor  part  load  efficiency  and  the  only  advantage  the  writer 
knows  of  is  that  it  is  more  nearly  water-tight  when  not  running 
than  is  the  wicket  gate  turbine. 

In  the  case  of  wicket  gates  it  is  common  practice  to  so  balance 
the  gates  that  there  is,  at  all  times,  a  tendency  to  close.  This 
is  so  that  in  case  of  accident  the  gates  will  stop  the  wheel.  This 
is  undoubtedly  a  mistake.  It  makes  governing  more  difficult, 


POWER  HOUSE  EQUIPMENT. 


361 


subjects  the  governor  to  unnecessary  load,  and  serves  no  useful 
purpose.  All  well-designed  plants  have  some  means  of  shutting 
off  the  water  and  in  case  anything  did  break,  the  penstocks,  or 
flumes,  could  be  emptied.  Water  wheels  cannot  quite  double 
their  normal  speed  when  racing,  and  therefore  the  danger  from 
the  centrifugal  force  bursting  the  fly-wheel  or  armature  is  not 
great.  With  perfectly  balanced  wicket  gates,  short  vertical 
draft  tubes,  proper  fly-wheel  effect,  and  an  open  setting,  we  need 
have  no  difficulty  in  obtaining,  practically,  perfect  government. 
The  Lombard  governor  Company  now  build  a  type  "  O  " 


FIGS.  363-364. 

governor  which  possesses  a  new  feature  of  great  merit.  The 
gates  are  closed  in  the  usual  way,  but  the  valves  are  so  arranged 
that  they  do  not  completely  close  at  first,  an  opening  of  about 
one  inch  being  left  to  prevent  water  hammer. 

Summing  up,  it  appears  that  a  governor  should  possess  the 
following  features: 

(1)  The  first  impulse  tending  to  set  the  governor  into  action 
should  come  from  the  ammeter  on  the  switchboard. 

(2)  The  governor  should  be  so  arranged  that  the  speed  may 
be  increased,  for  synchronizing,  from  the  switchboard. 

(3)  Where  the  energy  required  to  operate  the  gates  is  great, 
a  governor  of  the  hydraulic  type  should  give  the  best  service. 


362  HYDROELECTRIC  PLANTS. 

(4)  The  gate  moving  should  be  of  a  differential  character  so 
that  the  mechanism  will  not  be  subjected  to  excessive  strains. 

(5)  If  the  governor  is  set  in  motion  by  the  ammeter  it  should 
instantly  operate  on  a  variation  of  the  load,  but  if  of  the  types 
now  on  the  market,  the  governor  should  commence  acting  on 
a  variation  of  the  speed  of  the  line  shaft  of  J  per  cent,  from 
normal. 

(6)  The  governor  should  move  the  gates  through  their  full 
range  within  a  certain  time,  say  1.25  to  15  seconds. 

(7)  Under  steady  head  and  load  the  governor  should  remain 
stationary,  and  under  all  changes  of  load  it  should  not  make 
more  than   three  movements  in  readjusting  the  gate  to  the  new 
load  condition. 

(8)  The  governor  should  develop  a  definite  amount  of  energy. 

(9)  All  the  important  bearings  should  be  of  the  self-aligning 
self -oiling  type. 

In  the  above,  clauses  1,  3  and  5  are  by  the  author ;  2,  4  and  9  are 
by  Replogle;  6,  7  and  8  are  by  Sturgess. 

Referring  to  Fig.  362,  the  dotted  line  shows  the  gate  action 
when  the  impulse  to  act  comes  direct  from  the  ammeter.  The 
gate,  commencing  to  open  gradually,  gets  up  speed  and  then 
approaches  full  open  with  a  retarded  motion  at  which  point  the 
governor  begins  to  be  acted  upon  by  the  change  in  speed  of  the 
line  shaft  (if  there  is  a  change  in  speed),  and  assumes  control. 
The  special  ammeter  is  so  adjusted  that  if  the  change  of  load 
is  not  severe  the  gates  will  increase  the  opening  J  as  at  a,  and 
then  wait  for  the  governor.  If  quite  severe  they  open  §  as  at  b, 
and  for  unusually  heavy  changes  the  gates  are  moved  to  9/10 
opening.  In  case  of  loads  being  reduced  the  above  operation 
would,  of  course,  be  reversed. 

In  Fig.  362,  e  is  the  permanent  "  set,"'  of  the  regulation  and 
indicates  lack  of  proper  design.  If  the  turbines  are  properly 
proportional  in  speed  and  power  this  drop  will  not  take  place 
unless  the  penstock  is  long  and  small,  and  not  provided  with  a 
standpipe  in  which  case  it  may  take  a  minute  or  more  for  the 
water  throughout  the  entire  pipe  line  to  get  under  full  motion. 

If  we  could  pre-d^termine  the  curves  shown  in  Fig.  362, 
we  could  easily  design  the  fly-wheel  to  store  up  the  energy 
necessary  to  prevent  the  fall  in  speed  shown. 


POWER  HOUSE  EQUIPMENT.  363 

The  work  E  given  out  by  the  fly-wheel,  while  the  velocity 
falls  from  V4  to  V2 


_, 


where  w  =  the  equivalent  weight  of  all  revolving  parts  in 
pounds;  Vl  =  velocity  in  feet  per  second  of  the  weight  moving 
around  in  a  circle  of  an  average  radius  and  at  the  maximum 
speed  ;  F2  =  the  reduced  speed  in  feet  per  second  of  the  revolving 
weight. 

Therefore  if  we  take  as  an  example  the  curves  in  Fig.  362,  we 
find  that  the  average  drop  in  speed  for  eight  seconds  is  1.2  per  cent.  ; 
so,  if  the  normal  speed  is  10  revolutions  per  second,  the  average 
drop  is  .12  revolutions  per  second  for  eight  seconds.  To  carry 
the  added  load  of  50  h.p.  for  eight  seconds  the  fly-wheel  must 
give  out  50x33,000x8/60  foot  pounds  of  work  per  second  = 

w  (V  2  _  y  2\ 

220,000  =  -     —  -  >          2     .     After  getting  the  mean  radius  of  the 
t)4  .  4 

armature,  shafts  and  pulleys,  calculate  the  fly-wheel  effect. 
Say  that  this  is  found  to  be  20,000  foot  pounds  per  second, 
then  220,000  -  20,000  =  200,000  foot  pounds  to  be  supplied 
by  the  fly-wheel.  If  the  mean  diameter  of  the  fly-wheel  rim  is 
12  feet  and  the  maximum  revolutions  per  second  of  the  fly- 
wheel is  10,  then 

Vl  =  12X7TX10  =  377  feet  per  second;  and 

V2  =  12X7T  (10  -.12)  =  372+; 
then 


200,000  -  ~  3722)   -  3420  pounds. 


Therefore  a  fly-wheel  having  a  rim  weighing  3420  pounds 
would  have  prevented  the  fall  in  speed.  Of  course  this  would 
be  a  very  small  fly-wheel,  but  in  this  example  the  fall  in  speed 
was  slight  and  the  load  small. 

JFig.  365  shows  an  ideal  arrangement  of  standpipe  and  tur- 
bine unit.  The  penstock  is  continued  on  through  the  power 
house  and  ends  in  the  reservoir. 

Mr.  G.  A.  Buivinger  describes  such  a  plant.  Much  difficulty 
had  been  experienced  with  this  power  plant  due  to  long  pen- 
stocks (6200  feet  by  8  feet),  long  draft  tubes,  etc.  A  10,000 


364 


HYDROELECTRIC  PLANTS. 


pound  fly-wheel  was  placed  on  the  shaft,  and  while  this  aided 
the  regulation,  it  did  not  perceptibly  effect  the  pressures  on 
the  pipe.  Finally  a  reservoir  50  feet  in  diameter  and  12  feet 
deep  was  built  as  shown.  The  capacity  of  the  power  plant 
was  800  horse  power  under  47-foot  head,  and  this  reservoir 
supplied  2000  cubic  feet  of  water  for  each  foot  in  depth  and  there- 
fore one  foot  of  water  supplied  2000xG2.oX47  =5,875,000 
foot  pounds  per  minute  and  for  30  seconds  twice  that,  or  11,750,- 
000,  which  is  about  half  the  full  load  output  of  the  plant. 

This  arrangement  gives  the  water  in  the  penstock  a  free  path 
into  the   reservoir.     The  reservoir  can   frequently   be   built  of 


FIG.  365. 

concrete  on  top  of  a  near-by  cliff,  and  in  such  cases  (where  no 
tower  is  required)  there  should  be  no  limit  to  the  height.  The 
efforts  made  to  reduce  the  pressures  in  the  above  plant  by 
installing  a  10,000  pound  fly-wheel  would  indicate  that  the  re- 
lation between  pipe  pressures,  fly-wheel  and  regulation  is  not 
well  understood.  Water  hammer  can  not  be  prevented  by 
the  use  of  a  fly-wheel  and  the  present  day  governor.  The  gov- 
ernor acts  from  the  line  shaft  and  the  fly-wheel  retards  the 
action  of  the  governor.  The  presence  of  the  fly-wheel  would, 
other  things  being  equal,  permit  the  more  gradual  opening  of 
the  gates,  but  owing  to  the  fact  that  it  takes  longer  to  get 
the  line  shaft  up  to  speed  again  with  a  fly-wheel,  if  the  gates 
operate  slowly  the  result  will  be  that  the  speed  will  not  fall  so 


POWER  HOUSE  EQUIPMENT.  365 

low  but  the  period  will  be  increased  and  where  the  load  fluctuates 
rapidly  the  second  peak  may  come  before  speed  is  restored. 
Therefore  it  is  fully  as  important  to  have  quick  gate  action 
with  a  fly-wheel  as  it  is  without.  The  dash  and  dotted  line 
above  the  speed  curves  illustrates  the  effect  of  a  fly-wheel. 

The  only  safety  from  water  hammer  is  the  standpipe  or  relief 
valves. 

The  function  of  a  standpipe  is  not  to  take  the  place  of  the 
fly-wheel,  its  duty  being  to  prevent  water  hammer. 

Water  flowing  in  a  long  penstock  must  be  suddenly  arrested, 
the  doing  of  which  produces  a  bursting  tendency.  If  we  let 
P  equal  the  normal  working  pressure  per  square  inch  on  the 
penstock,  due  to  the  hydrostatic  head;  P1?  the  pressure  which 
will  be  produced  by  shutting  the  gates  a  certain  percentage 
of  the  opening,  v  =  the  velocity  in  feet  per  second  in  the  pipe 
at  the  time  the  gate  is  moved.  Then 
P!  =  i  (P  +  62.92  Xv)+Vi  (P  +  62.92  X?;)2- 62.92  XPX?;X£ 

p  =  the  percentage  of  the  normal  output  remaining  after  a 
reduction  of  load.  Thus  if  the  wheels  are  running  under  full 
load  and  half  the  load  is  thrown  off,  p  =  .50.  In  the  above, 
the  penstock  is  not  supposed  to  increase  in  volume  under  the 
pressures. 

Governing  High  Head  Systems. 

In  the  development  of  power  from  water  under  high  pressure, 
certain  .difficulties  arise  which  must  be  carefully  considered, 
else  disaster  will  follow.  As  already  explained  water  hammer 
is  a  great  danger  to  the  pipe  line.  It  has  been  stated  in  the 
preceding  pages  that  safety  valves  and  standpipes  were  the  two 
methods  employed  to  prevent  water  hammer.  The  following 
refers  to  heads  above  200  to  300  feet  where  standpipes  cannot 
be  employed. 

Where  tangential  wheels  are  used  and  the  head  too  great 
for  a  standpipe,  the  deflecting  needle  nozzle  serves  to  prevent 
water  hammer  and  gives  the  highest  efficiency  where  the  state 
laws  require  that  the  natural  flow  of  the  stream  be  uninterrupted. 
Here  the  waste  of  water  can  not.be  avoided,  but  where  it  is  pos- 
sible to  store  the  flow  during  light  loads  great  economy  is  de- 
sirable. In  this  case  the  needle  nozzle  shown  in  Fig.  366  gives 
the  highest  efficiency  and  the  best  regulation.  The  force  re- 
quired to  operate  this  nozzle  is  very  slight. 


366 


HYDROELECTRIC  PLANTS. 


POWER  HOUSE  EQUIPMENT.  367 

It  is  evident  that  when  the  needle  is  suddenly  thrust  outward 
water  hammer  is  produced.  To  relieve  this  excessive  pressure 
safety  valves  must  be  provided  and  as  there  is  no  more  im- 
portant part  of  the  power  equipment  it  should  be  carefully 
designed.  The  common  type  is  built  similar  to  the  safety 
valve  on  a  steam  engine  and  is  open  to  the  danger  of  sticking 
in  the  seal.  This  failure  to  operate  at  the  critical  time  has  caused 
the  loss  of  many  thousands  of  dollars.  To  be  safe  against 
sticking,  the  valve  should  be  made  to  rotate  constantly,  or  con- 
structed as  in  Fig.  366. 

In  this  safety  valve  water  stands  normally  at  some  level,  a, 
in  the  pipe,  b,  compressing  the  air  in  b.  As  the  pressure  in- 
creases the  water  rises  in  6,  till  the  hollow  ball  c  floats  up  and 
completes  the  circuit  between  the  switchboard  and  the  solenoid 
S,  thus  causing  the  balanced  valve  d  to  descend  and  the  valve  e 
to  open. 

Instead  of  operating  the  valve,  e,  this  same  arrangement 
could  be  used  to  deflect  the  nozzle.  The  governor  operates  the 
needle  at  g. 

TESTING. 

There  can  be  no  object  in  insisting  on  a  guarantee  for  a 
machine  unless  a  test  is  performed  to  ascertain  whether  the 
guarantee  has  been  made  good  or  not.  Such  tests  cost  a  good 
deal  and  it  is  seldom  indeed  that  large  turbines  are  tested  after 
being  guaranteed  and  placed. 

However,  if  a  test  shows  up  a  loss  of  a  few  per  cent,  on,  say, 
a  500  h.p.  turbine,  and  the  water  wheel  company  can  be  held 
for  this  loss,  the  amount  saved  will  more  than  pay  for  the  in- 
vestment. For  a  deficiency  of  five  per  cent.,  25  h.p.  would  be 
lost,  which  at  $20  means  $500  clear  cash  lost  each  year  and  at 
ten  cents  per  kw.-hr.  (3000  hours  per  annum),  would  mean  $5595. 

The  turbine  manufacturers  send  their  wheels,  that  is,  one  of 
each  pattern,  to  Lowell  or  Holyoke,  Mass.,  where  there  are 
companies  that  make  a  business  of  such  work.  However,  the 
engineer  in  charge  of  the  power  plant  should  from  the  start 
plan  to  make  a  test,  because  the  testing  flume  efficiency  is  seldom 
attained  in  practice. 

During  construction,  while  the  wheel  pit  is  free  from  water, 
a  weir  W,  Fig.  367,  should  be  put  in.  It  is  often  placed 


368 


HYDROELECTRIC  PLANTS. 


under  the  power  house,  but  usually  it  may  be  placed  fur- 
ther down  stream,  the  greater  the  distance  from  the  turbine 
the  better.  This  weir  should  be  so  constructed  that  after  the 
test  it  can  be  easily  removed.  If  it  is  necessary  to  put  the 
weir  close  to  the  wheels,  an  equalizing  rack  is  placed  parallel 
to  and  at  distance  of  five  or  six  feet  from  the  weir.  This  rack 
has  numerous  small  openings  equal  to  about  one-fourth  or  one- 
fifth  the  entire  area. 


FIG.  367. 


Fig.  367  shows  how  the  exact  depth  over  the  weir  is  obtained 
by  means  of  a  hook  gauge  and  a  water-tight  box  communi- 
cating through  a  f-inch  lead  pipe  with  head  water.  As  shown 
this  gauge  may  be  placed  above  the  equalizer  and  it  will 
give  the  same  reading  as  if  placed  below.  Air  must  be  ad- 
mitted under  the  overpour  at  V,  otherwise  the  formulas  given 
in  Chapter  II  will  give  too  large  a  flow. 

Fig.  369  shows  the  general  arrangement  of  the  friction  brake 
as  arranged  for  testing  a  vertical  turbine.  If  the  friction-pulley 
is  heavier  than  the  gear  ordinarily  used,  it  is  suspended  by 
means  of  cords  passing  over  pulleys  and  attached  to  counter 
weights.  This  is  a  refinement  which  would  not  be  necessary 


POWER  HOUSE  EQUIPMENT. 


369 


in  ordinary  tests.     The  brake  is  suspended  in  the  proper  position 
around  the  pulley  by  means  of  ropes  and  weights  W. 

A  bell  crank  C  is  used  to  transmit  the  turning  effort  from  the 
brake  arm  to  the  scales  (Fig.  369).  The  operation  is  best 
demonstrated  by  an  actual  example.  Let  the  dimensions  of 
the  bell  crank  C  be  M  =  5  feet  and  N  =  6  feet;  the  effective 
length  of  the  brake  lever  0,  Fig.  370,  be  10  feet.  Then  the 
total  leverage  acting  on  the  friction-pulley 

^   or  lt)xj  =  12ft. 


FIG.  359. 
and  the  total  force  acting  on  the  pulley  face  is 


W  O       =  10     W  =  12  W. 
M  o 

wherein  W  is  the  weight  as  measured  at  the  end  of  the  bell 
crank  arm  N. 

The  weight,  W  is  used  to  counter-balance  the  brake  rigging. 


The  power  of  the  turbine  = 


6.28X0XJFXr.p.m.      6.28X12X.20Q 


33,000 


33,000 


=  457  h.p.  where  6. 28  =  2?r,  0  =  effective  inches,  W=  weight  on 
scale  arm. 

At  the  start  everything  must  be  in  balance.  As  shown  in 
Fig.  369  the  bell  crank  is  the  heaviest  to  the  left  of  the  knife 
edge,  and  in  practice  an  arm  P,  would  be  attached  to  balance 


370 


HYDROELECTRIC  PLANTS. 


the  scale  pan,  etc.  The  friction  pulley  should  have  about  100 
square  inches  frictional  surface  per  h.p.,  and  may  be  from  18 
inches  to  120  inches  in  diameter.  Heavy  cylinder  oil  may 
be  used  as  a  lubricant,  however,  green  pig  fat  is  the  best. 

During  the  test  the  exact  head  is  obtained  by  getting  the 
level  of  the  water  over  the  wheels.     Then,  having  the  quantity 

HeadX62JxQ 

of  water  per    minute  the  i.h.p.  is  found  from * . 

oo,UUU 

The  h.p.  measured  with  the  brake,  divided  by  the  i.h.p.,  gives 
the  efficiency. 

Undoubtedly   one   of   the   best   all-around   dynamometers   is 
that  shown  in  Fig.  370.     This  dynamometer  has  been  thoroughly 


FIG.  370. 

tested  at  Purdue  University.  The  wood  shoes  are  placed  two 
or  three  inches  apart  and  are  fitted  to  the  face  of  the  pulley. 
Wrought  iron  straps  press  these  against  the  face. 

The  flanges  shown  in  the  part  sectional  view  are  intended 
to  hold  water  which  is  poured  in  for  cooling  purposes.  The 
Westinghouse  Company  have  found  that  for  piling  the  break 
shoes  "  green  "  pig  fat  is  the  best.  A  large  slice  is  laid  upon 
the  top  of  the  shoes  and  the"  heat  allowed  to  melt  it. 

To  get  the  proper  area  for  brake  shoes,  the  author  has  the 

following  formula:  A  =  ^     ^  ,  wherein  A  is  the  total 


POWER  HOUSE  EQUIPMENT.  371 

area  of  the  shoes  in  square  inches ;  P  the  power  in  horse  power 
to  be  dissipated;  S  the  speed  in  revolutions  per  min.,  and  R  the 
radius,  in  feet,  of  the  pulley. 

This  is  derived  from  dynamometers  actually  made  and  used 
by  various  engineers.  About  one-half  to  one-fourth  of  the  area 
of  the  pulley  face  should  be  covered  by  the  shoes. 

p 

For  brakes  not  cooled  by  water  use  A  = 


The  capacity  P  of  this  dynamometer  in  horse  power  (the  prin- 
ciple is  the  same  for  other  types)  is  found  from  the  following 
formula: 

Ififll  v  A  v  jh  v  7?  v  t*  TV  -»v» 
•  UU  J.  /\  ^1  XX  /'  /\  JV  /N  I  .  JJ.II1.  j— 

33,000  ' 

where  A  —  the  area  in  square  inches  of  the  frictional  surfaces 
of  all  the  shoes;  p  =  the  assumed  pressure  per  square  inch  of 
the  shoe  on  the  rim  of  the  wheel,  and  may  be  taken  at  about 
three  pounds.  1.001  is  a  constant  found  by  multiplying  the 
coefficient  of  friction,  .35,  by  TT;  R  is  the  radius  of  the  wheel 
in  feet. 

This  formula  must  not  be  confused  with  that  for  the  measure- 
ment of  the  power  as  in  that  case  R  is  the  radius  at  which  W 
is  applied  and  =  0,  Fig.  370.  It  is  only  used  to  get  at  the 
proper  size  of  the  brake. 

For  testing  large  turbines  a  less  expensive,  and  at  the  same 
time  a  very  satisfactory  way  is  to  test  the  electrical  generators 
driven  by  them.  Of  course  this  can  only  be  done  when  there 
is  direct  connection  as  the  efficiency  of  a  line  of  shafting  would 
otherwise  have  to  be  found. 

HYDRO-COMPRESSORS. 

No  book  on  hydraulics  would  be  complete  without  something 
on  hydro-compressors,  a  method  of  power  development  that 
is  to  become  quite  common  in  the  future. 

Fig.  371  shows  in  its  entirety  such  a  compressor.  The  letters 
show  the  important  parts  as  follows:  A,  the  penstock;  B,  the 
receiver;  C,  the  compressor  pipe ;  D,  the  air  chamber  or  collector; 
E  and  F,  the  tail. race;  G,  timbering  used,  where  shaft  is  sunk 
in  earth,  to  support  the  walls ;  77,  the  blow-off  pipe ;  7,  the  com- 
pressed air-feed  pipe;  /,  the  air  head  consisting  of;  a,  the  tel- 


372 


HYDROELECTRIC  PLANTS. 


w 

FIG.  371. — Hydro-compressor. 


POWER  HOUSE  EQUIPMENT.  373 

escoping  pipe  with  bell-mouthed  casting,  b,  opening  upwards; 
c,  the  cylindrical  and  conical  casting;  d,  the  vertical  air  supply 
pipes,  each  having  at  its  lower  end  a  number  of  smaller  inlet 
pipes  radiating  from  it  towards  the  center  of  compressor  pipe ; 
e,  the  adjusting  screws  for  raising  the  air-head;  K,  the  diffuser; 
L,  the  apron;  M,  the  pipes  to  allow  the  escape  of  air  from  be- 
neath apron  and  dispenser;  A/",  the  legs  by  which  the  separating 
tank  is  raised  above  the  bottom  of  the  shaft  to  allow  egress 
of  the  water.;  P,  the  automatic  regulating  valve. 

The  water  is  conveyed  to  the  tank  B  through  the  penstock 
A,  where  it  rises  to  the  same  level  as  the  source  of  supply.  In 
order  to  start  the  compressor  the  head  piece  /  must  be  lowered 
by  means  of  the  hand-wheel  /  so  that  the  water  may  be  ad- 
mitted between  the  two  castings  b  and  c.  The  supply  of  water 
to  the  compressor,  and  consequently  the  quantity  of  com- 
pressed air  obtained,  is  governed  by  the  depth  to  which  the  head 
piece  is  lowered  into  the  water.  The  water  enters  the  com- 
pressing pipe  between  the  two  castings  b  and  c,  passing  among, 
and  in  the  same  direction  as,  the  small  air  inlet  pipes  d.  A 
partial  vacuum  is  created  by  the  water  at  the  ends  of  these  small 
pipes,  and  hence  atmospheric  pressure  drives  the  air  into  the 
water  in  innumerable  small  bubbles,  which  are  carried  by  the 
water  down  the  compressing  pipe  C.  During  their  downward 
course  with  th~  water  the  bubbles  are  compressed,  the  final 
pressure  being  proportional  to  the  column  of  water  sustained 
in  the  shaft  E  and  tail  race  F. 

When  they  reach  the  disperser  K  their  motion  is  changed, 
along  with  that  of  the  water,  from  the  vertical  to  the  horizontal. 
The  disperser  directs  the  mixed  water  and  air  towards  the 
circumference  of  the  separating  tank  D.  Its  direction  is  changed 
again  towards  the  center  by  the  apron  L.  From  thence  the 
water  flows  upward,  and,  free  of  air,  passes  under  the  lower 
edge  of  the  separating  tank.  During  this  process  of  travel  in 
the  separating  tank,  whiqii  is  slow  compared  with  the  motion 
in  the  compressing  pipe  C,  the  air,  by  its  buoyancy,  has  been 
rising  through  the  water  and  pipes  M,  M,  from  under  the 
apron  and  disperser,  to  the  top  of  the  air  chamber  D,  where  it 
displaces  the  water.  The  air  in  the  chamber  is  kept  under  a 
nearly  uniform  pressure  by  the  weight  of  the  return  water  in 
the  shaft  and  tail  race. 


374  HYDROELECTRIC  PLANTS. 

The  air  is  conveyed  through  the  main  7,  up  the  shaft  to  an 
automatic  regulating  valve,  and  from  thence  to  the  engines, 
etc.  The  air  pressure  in  the  main  and  air  chamber  increases 
one  pound  per  square  inch  for  each  two  feet  three  and  a  half 
inches  that  the  water  is  displaced  downwards  in  the  air  chamber 
by  the  accumulating  air.  The  variation  in  pressure  from  this 
source  will  not  be  more  than  three  pounds  per  square  inch  in  a 
working  plant.  As  the  automatic  valve  requires  a  change  of 
only  one  pound  per  square  inch  pressure  to  close  it  completely 
it  will  be  evident  that,  by  properly  adjusting  the  valve,  some 
air  can  always  be  retained  in  the  air  chamber,  and  that  the 
water  can  be  prevented  from  ever  reaching  the  inlet  to  the  air 
main. 

If  a  large  quantity  of  air  has  accumulated  in  the  air  chamber, 
the  valve  allows  of  its  free  passage  along  the  main;  but  when 
the  air  is  being  used  more  quickly  than  it  is  accumulating, 
and  the  pressure  decreases  below  a  certain  point  because  the 
chamber  is  nearly  emptied  of  air,  the  valve  shuts  partially, 
or  completely,  adjusting  itself  to  the  supply  from  the  compressor. 
When  the  air  has  displaced  the  water  almost  to  the  lower  end 
of  the  compressing  pipe,  it  escapes  through  blow-off  pipe  H. 
A  hydro-compressor  was  built  at  Magog,  P.  Q.,  and  tested  by  a 
number  of  experts  and  was  found  to  have  an  efficiency  in  re- 
lation to  the  power  of  the  falling  water  of  from  55  to  71  per  cent. 
An  old  steam  engine  driven  with  the  compressed  air  gave  51.2 
h.p.  for  each  100  h.p.  in  the  falling  water.  When  the  compressed 
air  was  heated  to  267  degrees  F.,  the  efficiency  was  61.5  per 
cent.  If  this  heated  compressed  air  had  been  used  in  a  modern 
hot  air  jacket  engine  the  efficiency  would  have  been  87J  per 
cent. 

Another  compressor  at  Ainsworth,  B.  C.,  gave  71  per  cent, 
efficiency.  Much  depends  on  the  number  of  the  air  pipes  and 
the  air-head  should  be  so  made  that  pipes  may  be  added  or 
taken  out.  The  number  should  be  greatest  when  about  half 
the  water  is  used  and  reduced  at  full  flow. 

A  new  and  very  large  compressor  plant  is  that  located  at 
Victoria  Mines  in  Michigan.  The  author  is  indebted  to  Mr.  W.  O. 
Webber  for  the  following  data: 

The  minimum  quantity  of  water  available  is  29,000  cubic  feet 
a  minute.  The  power  available  is  4000  h.p. ;  the  dam  is  28 


POWER  HOUSE  EQUIPMENT. 


375 


feet  in  height,  and  is  a  mile  above  the  site  of  the  compressor, 
and  the  extreme  height  from  the  top  of  the  dam  to  the  outlet 
of  the  compressor  is  72  feet.  There  are  three  downflow  pipes 
in  solid  rock,  5  feet  in  diameter,  and  334  feet  deep;  they  are 
lined  with  6  inches  of  concrete.  The  air  chamber  at  the  bottom 
has  a  capacity  of  82,000  cubic  feet  of  air.  The  surface  pipe  is 
24  feet  in  diameter,  and  the  blow-off  pipe  12  inches  in  diameter. 
Each  one  of  the  downflow  shafts  can  be  operated  independently, 
and  furnishes  an  equivalent  of  1300  h.p.  The  air  is  furnished 
at  a  pressure  of  118  pounds  per  square  inch.  The  total  cost 
of  compressor,  including  dam,  was  $200,000. 

The  water  is  received  into  the  downflow  shafts  over  a  cir- 
cular shaped  apron  five  feet  in  diameter.     The  apron  is  of  steel 

TABLE  XLI 
DATA  FROM  EXISTING  HYDRO-COMPRESSORS. 


H.P. 

developed. 

Diam  of. 
tube, 
inches. 

Diam.  of 
shaft, 
feet. 

Gauge 
press, 
pounds. 

Head, 
feet. 

Depth  of 
shaft, 
feet. 

Location  of  Plant. 

587 

33 

7. 

46 

107 

210 

Ainsworth,  B.  C. 

300 

18 

3.5 

25 

14 

64 

Petersborough,  Canada. 

150 

44 

7. 

52 

16 

150 

Magog,  P.  Q. 

1500 

168 

24 

91 

18.5 

240 

Norwich,  Conn. 

4000 

eat 

60 

118 

72 

334 

Victoria  Mine%  Mich. 

t  There  are  three  of  these  5-foot  tubes. 

construction,  and  weighs  11  tons.  Five  iron  pipes,  six  inches 
in  diameter,  extend  above  the  water  to  a  distance  of  four  feet, 
and  connect  several  inches  below  the  water  line  with  2000  small 
pipes,  0.25  inches  in  diameter,  each  small  pipe  pointing  toward 
the  center  of  the  apron.  The  small  pipes  are  about  18  inches 
in  length,  and,  being  arranged  in  a  circle,  there  remains  a  space 
in  the  center  of  the  shaft  3.5  feet  in  diameter. 

As  the  water  flows  into  the  shaft,  air  is  drawn  down  through 
the  larger  pipes,  and  is  forced  into  the  water  as  it  passes  over 
the  ends  of  the  small  pipes.  The  separating  chamber  and 
separator  consists  of  expanding  tubes  downwardly  projecting 
into  the  air  chamber,  with  conical  concrete  diffusers  formed 
on  the  floor  of  the  separator  chamber  below  them. 

It  must  not  be  supposed  that  the  compressor  pipe  has  in  all 


376 


HYDROELECTRIC  PLANTS. 


cases  to  be  placed  in  a  well.  It  may  take  the  form  shown  in 
Fig.  372. 

Frizell  obtained  an  efficiency  of  52  per  cent,  under  a  5-foot 
head.  The  compressor  is  especially  adapted  to  low  heads. 

In  designing  a  compressor  the  head  and  quantity  of  water 
being  given,  first  decide  on  the  pressure  for  the  air.  Of  course 
the  higher  the  pressure  the  cheaper  the  engines  and  pipe  line, 
but  the  efficiency  of  the  compressor  is  less  for  high  pressures. 
The  loss  due  to  absorption  of  air  by  the  water  averages  about 
four  per  cent,  and  varies  as  the  square  of  the  pressure. 


FIG.  372. 

About  80  pounds  pressure  per  square  inch  should  be  at- 
tained, though  the  costs  of  all  the  various  machines  will  have 
to  be  the  determining  factor.  Having  decided  on  the  pressure, 
find  the  length  of  the  compressor  pipe  C,  by  multiplying  the 
pressure  by  2.3,  which  gives  the  length  in  feet.  The  diameter 
of  this  pipe  depends  on  the  volume  of  the  water  and  the  amount 
of  head  which  can  be  lost.  Its  diameter  is  figured  in  the  same 
way  as  that  of  a  penstock.  See  pages  26  and  199.  The  effective 
head  acting  on  this  pipe  is  that  due  to  the  difference  between'  the 
head  and  tail  water  levels,  minus  the  head  lost  by  the  water 
ascending  the  shaft.  The  velocity  in  the  shaft  E  should  not 
exceed  four  feet  per  second. 


POWER  HOUSE  EQUIPMENT.  377 

.  The  diameter  of  the  air  reservoir  or  collector  is  more  a  matter 
of  judgment,  but  its  area  may  be  from  10  to  15  times  that  of 
the  compressor  pipe. 

The  air  mixing  pipes  d  may  be  of  gas  pipe  of  from  f-inches 
to  two  inches  in  diameter  and  having  radial  pipes  as  shown  in 
Fig.  373.  The  holes  in  the  radial  pipes  are  on  the  underside 
so  that  the  water  falling  about  them  sucks  the  air  down  and 
out  of  the  pipes. 

Fig.  374  shows  the  Norwich  compressor.  The  air  head  is  mounted 
on  a  pipe  which  telescopes  into  the  compressor  pipe  allowing 
an  up  and  down  movement  equal  to  the  variation  of  the  level 
of  head  water.  Where  the  fluctuations  are  more  than  a  foot 
or  so  the  level  should  be  controlled  at  the  head  gates.  The 
same  head  gates  and  racks  suitable  for  a  turbine  plant  are  used 


FIG.  373. 

for  a  hydro-compressor,  the  rack,  however,  having  a  fine  brass 
wire  screen  to  catch  every  particle  of  drift.  That  part  of  the 
steel  work  containing  the  compressed  air  must  be  air-tight. 
The  receiver  must  be  protected  from  the  cold  in  the  northern 
climates  as  the  air  inlet  pipes  will  freeze  solid  when  the  com- 
pressor shuts  down. 

Where  the  water  used  exceeds,  say  six  to  ten  thousand  cubic 
feet  per  minute  the  plant  should  be  divided  up  into  units,  there 
being  a  common  shaft  and  air  chamber,  but  separate  compressor 
pipes,  receivers,  diffusers  and  aprons.  To  avoid  obstructing  the 
flow. as  much  as  possible  the  author  would  suggest  as  arrange- 
ment of  inlet  pipes  as  shown  in  Fig.  375,  the  pipes  being  open  at 
both  ends  and  also  having  small  holes  drilled  at  the  lower  ends. 
The  curve  in  the  pipes  corresponds  to  the  flow  of  the  falling  water, 
so  that  the  water  runs  along  instead  of  against  them. 


378 


HYDROELECTRIC  PLANTS. 


By  passing  the  compressed  air  through  a  heater  and  raising 
it  to  about  300  degrees  Fahrenheit,  50  per  cent,  more  power 
is  obtained.  To  do  this,  according  to  Mr.  Wm.  Webber,  requires 


FIG.  374. 

about  7J  per  cent,  of  the  power  in  the  river,  figured  on  the  basis 
of  the  amount  of  coal  used. 

Moistening  the  dry  compressed  air  in  the  engine  cylinder  also 


POWER  HOUSE  EQUIPMENT. 


379 


adds  to  the  power.  To  saturate  the  air,  the  water  has  to  be 
forced  into  the  engine  cylinder  against  the  air  pressure.  Each 
h.p.  in  the  river  requires  about  3.7  pounds  per  minute  of  water 
for  this  saturation,  and  the  work  performed  by  the  pumps  is 

-  (P  X  W  X  3.7)2 

tound        by       : — QQ  nnn —  =  power     required,      where 


p  _ 


33,000 

Pressure  of  air  in  Receiver 
.434 


and  W  is  the  theoretical  horse- 


power of  river.  The  minuend  is  multiplied  by  two  as  the 
efficiency  of  a  pump  is  about  50  per  cent.  The  power  thus  found 
is  about  4J  per  cent,  of  the  river  power. 

It  only  requires  a  glance  at  a  compressor  to  see  that  as  com- 
pared with  a  turbine  plant  it  is  simplicity  itself.  There  are  no 
moving  parts  to  wear  out.  No  expensive  and  troublesome 
governors  are  required.  No  attendance.  No  oil  or  wear.  No 


FIG.  375. 

fire  insurance,  and  practically  no  depreciation.  Everything  is 
automatic  and  it  can  be  built  under  any  and  all  conditions  of 
foundation. 

Professor  Unwin  states  that  it  is  practical  to  transmit  power 
by  compressed  air  to  a  distance  of  20  miles  with  a  loss  of  12  per 
cent. 

The  cost  is  less  than  a  turbine  plant,  as  there  are  no  journals, 
shafting,  gearing,  etc.,  the  only  cost  being  for  the  boiler  iron 
and  excavation.  The  cost  of  excavation  will  of  course  vary 
with  the  condition.  Rock  excavation  will  cost  $5  to  $8  per 
cubic  yard  and  earth  from  50  cents  to  $3. 

Mr.  Webber  places  the  cost  of  a  5,000  h.p.  compressor  at 
$42,000.  The  boiler  iron  ought  not  to  cost  more  than  four  cents 
per  pound  erected.  Of  course  the  same  dam,  head  gates,  canals 


380  HYDROELECTRIC  PLANTS. 

and  racks  are  required  as  for  a  turbine  plant,  but  no  power  house. 
For  distances  less  than  five  or  six  miles  (and  no  doubt  the 
future  will  see  this  increased),  the  transmission  of  the  power 
by  means  of  compressed  air  is  as  efficient  as  by  any  other  means, 
a  two  per  cent,  loss  being  usually  allowed.  A  velocity  of  60 
feet  per  second,  may  be  allowed  in  the  pipes, 'and  as  each  horse- 
power at  85  pounds  pressure  takes  about  1.44  cubic  feet  of 
air  per  minute,  the  area  of  the  pipe  may  be  determined.  Webber 
gives  the  cost  of  a  20-inch  steel  pipe  four  miles  long  carrying 
5,000  horse  power  at  85  pounds  pressure  as  $3.05  per  foot  laid, 
making  the  cost  per  mile  $18,500,  and  for  four  miles  $74,000. 
An  electric  transmission  would  cost  as  follows: 

Two  governors  (for  two  units) $2,000 

Generator  house 5,000 

Switch  board 2,000 

Four  miles  transmission  line 4,500 

Generators  and  exciters.  . 50,000 

Step  up  and  step  down  transformers.  .  .  .  30,000 


$93,000 

The  cost  is  more  in  favor  of  the  hydro-compressor  plant, 
as  the  distance  grows  less  and  vice  versa. 

Compressed  air  may  be  used  in  the  engines  already  operating 
a  factory,  but  the  greatest  efficiency  is  obtained  when  each 
machine  is  driven  by  its  own  air  engine,  in  which  case  the  effi- 
ciency is  about  that  of  the  electric  motor. 

Water  is  sprayed  into  the  cylinder  of  the  air  engine,  but  any 
engine  may  be  fitted  with  a  spray. 

Small  air  motors  of  about  \  h.p.  require  as  high  as  14  cubic 
feet  of  air  at  80  pounds  pressure  per  square  inch  per  minute  per 
horse  power. 

AUXILIARY  PLANTS. 

The  same  course  of  reasoning  as  applied  to  a  storage  battery 
plant,  see  page  421,  should  be  pursued  in  selecting  the  proper 
size  of  the  auxiliary  plant,  the  chief  difference  being  that  the 
auxiliary  plant  is  used  to  tide  over  the  months  of  low  water 
rather  than  the  daily  fluctuations  of  load,  and  the  curves  show- 
ing the  monthly  fluctuations  of  the  river  flow  are  used  in  de- 
termining the  proper  size  of  the  plant  rather  than  the  hourly 


POWER  HOUSE  EQUIPMENT. 


381 


Variations  in  the  power  output.  Usually  the  size  of  the  auxiliary 
has  to  be  guessed  at,  as  accurate  data  on  the  river  flow  is  seldom 
to  be  had. 

STEAM    PLANT. 

Boilers. 

In  considering  an  auxiliary  plant  for  a  water  power  it  must 
be  borne  in  mind  that  ordinarily  it  will  be  in  use  but  about  one- 
third  of  the  time.  Therefore  a  boiler  should  be  selected  which 
will  depreciate  the  least  when  not  in  use.  The  kind  of  boiler 
selected  should  next  depend  upon  the  price  of  coal. 

Table  XLII  gives  relative  economy,  etc.,  of  the  various  types 
of  boilers. 


TABLE  XLII. 
COMPARISON  OF  VARIOUS  TYPES  OP  BOILERS. 


Type  of  Boiler. 

Sq.  ft.  of 
heating 
surface 
for  1  h.p. 

Coal  per 
sq.  ft. 
Heating 
Surface 
per  hour. 

Relative 
economy. 

Relative 
Rapidity 
of  steaming. 

Authority. 

Water-tube  
Tubular   . 

10  to  12 
14  to  18 

.3 
25 

1.00 
91 

1.00 
50 

Isherwood. 

Flue  

8  to  12 

.4 

.79 

.25 

Prof.  Trowbridge 

Plain  Cylinder  

6  to  10 

.5 

.69 

.20 

Locomotive  

12  to  16 

.275 

.85 

.55 

Vertical  Tubular  

15  to  20 

25 

.80 

.60 

In  actual  practice,  all  day  firing,  and  for  small  lighting  plants 
having  compound  condensing  engines,  10  pounds  of  coal  is 
burned  for  each  kw-hr  at  the  switch  board.  In  badly  designed, 
small,  isolated  plants  the  consumption  may  reach  15  pounds 
per  kw-hr. 

The  coal  item  is  about  half  the  entire  cost  of  steam 
power.  A  locomotive  boiler  will  evaporate  (usual  practice) 
from  6  to  8  pounds  water  per  pound  of  coal,  while  a 
water  tube  boiler  will  evaporate  7J  to  9  pounds.  Therefore, 
if  we  wish  to  install  a  1000  h.p.  boiler  plant  where  fair  coal  costs 
$1  per  ton  (2240  pounds  is  always  considered  a  ton  of  steam 
coal),  and  where  the  plant  will  be  run  1000  hours  per  season  of 


382 


HYDROELECTRIC  PLANTS. 


drought,  the  value  of  the  difference  between  the  coal  used  by 
the  water  tube  and  the  locomotive  boilers  is  first  determined. 

TABLE  XLIII. 
FUEL  AND  WATER  REQUIRED  FOR  THE  PRODUCTION  OF  MECHANICAL  ENERGY. 


Lbs.  water  from  and  at 
212°  per  Ib.  of  coal. 

Lbs.  coal  per 
h  p.  per  hour. 

9 

3.83 

Good  coal  and  boiler 

10 

3.45 

Fair  coal  and  boiler 

8.6 

4. 

8. 

4.31 

7. 

4.93 

Poor  coal  and  boiler 

7. 

5. 

6. 

5.75 

5. 

6.90 

Lignite  and  poor  boiler. 

3.5 

10. 

From  Table  XLIII  it  is  seen  that  for  a  first  class  boiler  of 
the  water  tube  type  about  3 . 7  pounds,  of  coal  will  be  used  per 
h.p.  per  hour,  and  1000  h.p.  for  1000  hours  will  use 

1,000,000X3.7 


which,    at      $1,    will 
will    consume    about 

or  in  the  above  case 


2240 

cost    $1,652. 
six    pounds    of 

1,000,000X6 


1652  tons 

A     locomotive      boiler 
fair    coal    per    h.p.-hr., 


=  2,680  tons  costing  $2,680. 


Table  XLII  also  gives  the  relative  efficiencies  for  the  same  coal. 
The  water  tube  boilers  will   cost,  set  up,  about  $10,000,  not 
counting  buildings  or  smoke  stacks,  as  they  would  cost  about 
the  same  for  all  boilers,  except  where  building  sites  are  very 
expensive  and  fine  buildings  are  erected.     The  locomotive  boilers 
would  cost  about  $7000.     The  difference  in  cost  of  operation  is 
about  $1000  per  season  in  favor  of  the  water  tube  boilers,  airi 
difference  in  cost  of  plant  is  as  follows: 

Difference  in  first  cost  ..................      $3,000 

'  interest  on  investment  ......  180 

"  "maintenance..  300 


Total $3,480 


v 


POWER  HOUSE  EQUIPMENT. 


383 


About  3J  to  4  years  service  would  pay  for  a  first  class  boiler 
plant  if  the  coal  cost  $3.  In  one  season's  run,  the  water  tube 
boilers  would  save  $3000  over  the  cheaper  boiler,  an  amount 
which  just  pays  the  difference  in  their  cost. 

Another  strong  argument  for  the  water  tube  boiler  is  its  free- 
dom from  disastrous  explosions  and  ease  of  repair. 

The  author  would  strongly  advise  the  intending  purchaser  to 
look  up  the  second-hand  boiler  market.  Frequently  half  the 
cost  of  a  new  boiler  plant  can  be  saved  by  the  use  of  a  second- 
hand boiler,  which  is  practically  as  good  as  new.  Of  course 
great  care  must  be  taken  in  selecting  such  boilers.  The  Babcock 
&  Wilcox  and  the  Heine  water  tube  boilers  are  among  the  best. 

Table  XLV  and  diagram  will  give  a  good  idea  of  the  dimen- 
sions of  a  boiler  plant.  The  general  proportions  will  hold  good 
for  any  number  of  fire  tube  boilers.  The  setting  shown  is  of 
brick,  but  it  may  readily  be  made  of  concrete,  using  the  same 
dimensions.  The  setting  is  for  tubular  boilers ;  water  tube  boilers 
are  taller,  but  will  take  up  about  the  same  floor  space. 

It  is  impossible  to  give  the  table  of  sizes  for  water  tube  boilers, 
as  the  various  types  vary  so  widely,  but  below  is  given  the  rela- 
tive dimensions  of  three  of  the  most  prominent  makes: 

TABLE  XLIV. 
OUTSIDE  DIMENSIONS  OF  WATER  TUBE  BOILERS. 


Make  and  Nominal  Rated  Size  of  Boiler. 

Width. 

Length. 

Height. 

Babcock  &  Wilcox,  370  h.p  
Babcock  &  Wilcox   2  in  battery 

13'—  8" 
26'  —  6" 

17'—  9i" 
17  /  —  g^" 

19'—  6" 
19'  —  6" 

Sterling  500  h  p 

lg>  —  o" 

ig/  —  Q" 

23'  —  0" 

Babcock  &  Wilcox 

15'  —  5" 

23'  —  5" 

20'  —  0" 

Vertical  Wickes,  400  h.p  

22'—  11" 

19'—  5" 

34'—  0" 

Roughly,  each  horse  power  requires  about  0.666  square  foot 
of  floor  space. 

The  volume  occupied  by  water  tube  boilers  is  about  as  follows, 
for  the  largest  sizes: 

VOLUME  OF  WATER  TUBE  BOILERS  PER  H.P. 

Babcox  &  Wilcox 13. 75  cubic  feet 

Sterling 15.73      " 

Wickes..  18.70      " 


384 


HYDROELECTRIC  PLANTS. 


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POWER  HOUSE  EQUIPMENT. 


385 


The  capacity  of  the  boiler  plant  is  found  for  all  ordinary  loads 
as  follows: 

The  kilowatt  capacity  of  generators  times  0  75  equals  horse 
power  of  the  boilers.  Nominal  rating  is  used  in  above ,  of  course, 
where  a  water  power  is  to  take  all  the  peak  loads  this  would 


give  too  much.  Then  one-half  the  kilowatt  capacity  of  gen- 
erators would  be  sufficient. 

By  heating  the  feed  water  with  the  exhaust  about  6  to  10  per 
cent,  of  the  fuel  will  be  saved,  besides  saving  the  boilers  from 
the  evil  effects  of  filling  with  cold  water. 

If  slack  coal  is  used  it  should  be  blown  into  the  furnace. 


386 


HYDROELECTRIC  PLANTS. 


The  boiler  house  should  be  separated  from  all  other  rooms 
by  a  thin  wall. 

In  most  cases  steel  smoke  stacks  will  -be  found  the  most  eco- 
nomical for  an  auxiliary  plant.  There  should  be  at  least  two 
for  plants  of  any  size,  and  for  large  plants  about  one  stack  per 
1000  h.p.  One  stack  for  1000  h.p.  will  cost,  all  set  up,  about 
$1,500,  and  for  500  h.p.,  $500.  A  Weber  reinforced  concrete 
chimney,  10  feet  inside  diameter,  and  200  feet  high,  with  founda- 
tion, will  cost  about  $7,000. 


TABLE  XLVI  (Kent). 
SIZE  OF  CHIMNEYS  AND  PROPER  H.P.  BOILER. 


Height  of  Chimney  in  Feet. 

Diam.  of 

j 

chimney 

50 

60 

70 

80 

90 

100 

110 

125 

150 

"  £*Vip«; 

Commercial  H.P. 

18 

23 

25 

27 

21 

35 

38 

41 

24 

49 

54 

58 

62 

27 

65 

72 

78 

83 

30 

84 

92 

100 

107 

113 

33 

115 

125 

133 

141 

36 

141 

152 

163 

173 

182 

39 

183 

196 

208 

219 

42 

216 

231 

245 

258 

271 

, 

48 

311 

330 

348 

365 

389 

54 

363 

427 

449 

472 

503 

551 

60 

505 

539 

565 

593 

632 

692 

66 

658 

694 

728 

776 

849 

72 

792 

835 

876 

934 

1023 

78 

995 

1038 

1107 

1212 

84 

1163 

1214 

1294 

14^8 

90 

1344 

1415 

1496 

1639 

96 

1537 

1616 

1720 

1876 

The  quality  of  the  coal  has  much  to  do  with  the  size  of  the 
chimney.  The  height  should  be  about  75  feet  for  free  burning 
bituminous  coal,  115  feet  for  slow  burning  bituminous  coal  or 
slack,  and  125  to  150  feet  for  anthracite. 

The  steel  stack  rests  on  a  concrete  or  masonry  foundation 
and  should  be  bolted  firmly  to  it.  Galvanized  iron  cable  is 
used  to  guy  the  stack  and  these  and  the  anchorage  should  be 
designed  to  withstand  a  wind  pressure  of  25  pounds  per  square 
foot  against  the  stack.  Suppose  we  have  the  case  shown  in 


POWER  HOUSE  EQUIPMENT. 


387 


Fig.  377.  The  guys,  supposing  there  are  four,  will  support 
68  lineal  feet  of  the  pipe  against  the  wind  pressure  or  a  pressure  of 
5X60X25  =  7,500  pounds. 

If  the  guy  is  at  an  angle  of  45  degrees  the  tension  will  be 

7,500  x2  since  the  tension  is  proportional  to  the  distance    „ 

D  L 

therefore  the  cable  will  have  to  sustain  15,000  pounds  (see 
Table  LXIII).  This  is  more  than  would  be  ordinarily  given  to 
one  guy,  as  another  set  would  be  attached  further  down,  but 
the  above  will  serve  to  caution  the  builder  against  the  usual 
practice  of  using  any  and  all  kinds  of  anchorage  and  cables,  in 
the  blind  hope  that  no  great  storm  will  strike  the  stack. 

A  good  boiler  should,  under  forced  firing,  be  capable  of  evapo- 


rating twice  normal.  Therefore  in  selecting  the  proper  capacity 
of  the  boiler  plant  take  the  peak  load,  as  found  on  page  426,  and 
make  the  boiler  capacity  one-half  the  peak.  Boilers  should  be 
operated  25  per  cent,  above  the  rated  capacity  to  give  best  results. 

It  often  occurs  in  the  case  of  a  water  plant,  that,  while  there 
is  not  enough  water  to  carry  the  average  load  there  is  enough, 
using  a  storage  reservoir,  to  carry  the  peak  loads. 

In  this  case  the  water  is  all  reserved  for  the  peaks  and  the 
boilers  run  steadily  and  efficiently  on  the  average  load.  In 
which  case  the  capacity  of  the  boilers  is  made  equal  to  three- 
fourths  the  average  load. 

In  a  large  plant  there  should  always  be  at  least  one  spare  boiler. 
The  feeding  should  not  be  left  to  an  injector  alone,  but  both  an 
injector  and  a  pump  should  be  used  in  all  cases. 


388 


HYDROELECTRIC  PLANTS. 


Steam  Engines. 

The  engine  best  fitted  for  auxiliary  work  is,  undoubtedly,  the 
high-speed  automatic  cut-off  engine,  though,  as  in  the  case  of 
boilers,  the  price  of  coal  has  much  to  do  with  the  selection. 


TABLE  XLVII. 
COMPARATIVE  EFFICIENCV  OF  ENGINES. 


Kind  of  Engine. 

H.P. 

Steam 
Press. 

Water  per 
I.H.P..  non- 
condensing. 

Per  hour, 
condensing 

Plain  slide  valve  with  long  ^troke, 
cut-off  f  

25  to  100 

75  to    80 

40  to  50 

30  to  40 

Automatic,  high  speed,  single  valve, 
cut-off  J  

50  to  150 

75  to    80 

25  to  35 

20  to  25 

Automatic,  four  valve,  and  Corliss, 
high  speed,  cut-off  1/5  

50  to  500 

110  to  120 

22  to  30 

16  to  24 

Compound  automatic,  four  valve 
and  Corliss,  high  speed  

400  and  up 

110  to  120 

20  to  27 

13  to  20 

Triple  expansion  

500  an  1  up 

120  to  160 

20  to  27 

12?  to  18 

The  true  criterion  of  the  engine's  efficiency  is  the  amount  of 
water  used  per  i.h.p. 

<  By  use  of  the  above  table  in  connection  with  Table  XLIII  it 
can  be  easily  figured  what  the  coal  bill  will  be  with  the  different 
engines.  Of  course  the  less  efficient  engine  will  require  more 
boiler  capacity,  and  this  must  be  allowed  for. 

The  high-speed  engine  governs  to  within  2  per  cent  from 
normal  load  to  a  sudden  no  load.  Where  space  is  valuable  they 
are  the  thing,  especially  those  of  the  vertical  type,  such  as  the 
Westinghouse.  When  not  compounded  they  consume  about 
35  pounds  of  water  per  indicated  h.p.  per  hr. 

Roughly,  a  high-speed  automatic  cut-off  engine  will  cost  $14 
to  $17  per  h.p.,  all  set  up.  A  Corliss  cross  compound  slow-speed 
high-pressure  engine  will  cost  all  set  up  about  $30  to  $40. 

Usually  second-hand  engines  may  be  purchased  at  half  price, 
which  will  answer  every  purpose. 

As  the  engine's  power  is  given  by  the  formula 


H.P. 


2PLAN 
33,000 


where  P  is  the  mean  effective  steam  pressure  in  pounds  per  square 
inch  on  piston,  A  the  area  of  the  piston  in  square  inches,  A^  the 


POWER  HOUSE  EQUIPMENT.  389 

number  revolutions  per  minute,  and  L  length  of  the  stroke  in 
feet,  it  is  evident  that  by  varying  the  cut-off  and  therefore  P, 
the  power  of  the  engine  can  be  varied. 

All  engines  are  designed  for  a  certain  mean  effective  pressure, 
at  which  they  are  most  efficient,  and  in  selecting  the  proper  size 
its  capacity  should  just  equal  the  average  load,  unless  the  per- 
missible change  in  cut-off  for  the  particular  engine  will  not 
increase  the  power  sufficiently  to  take  care  of  the  peak  load. 
Suppose  the  case  of  a  100  h.p.  engine  cutting  off  at  J  stroke, 
boiler  pressure  at  100  pounds;  r.p.m.  =  250,  length  of  stroke 
L  =  1  foot,  and  the  area  of  the  cylinder  =  113  square  inches. 

Then  at  J  cut-off      2£  ^  N     =  102  h.p.      And    at    }    cut-off 


2PLAN 
33,000 

Boiler  pressure  multiplied  by  C  taken  from  table  XLVIII  is  sub- 
stituted in  the  above  for  Pin  each  case.  By  changing  the  cut-off 
from  J  to  J  we  add  about  50  per  cent  to  the  engine's  capacity. 
While  this  is  at  the  expense  of  efficiency,  it  will  be  good  practice 
to  make  165  h.p.  the  peak  load  capacity  of  the  engine.  Even 
|  cut-off  is  advisable  in  this  case.  Engines  having  heavy  fly- 
wheels can  carry  a  100  per  cent,  overload  for  a  few  seconds. 
As  in  the  case  of  boilers,  where  possible,  let  the  water  power 
take  care  of  the  peak  loads  and  keep  the  engines  working  as 
nearly  as  possible  at  full  load  and  efficient  cut-off. 

TABLE    XLVIII. 
MEAN  EFFECTIVE  PRESSURE  FOR  DIFFERENT  CUT-OFFS. 

Point  of  cut-off         C  Point  of  cut-off  C 

i  .5965                   |  .9188 

J  .6995                   §  .9370 

i  .7428                   f  .9657 

i  .8465                   J  .9917 

Boiler  pressure   X  C  =  Mean  Effective  Pressure. 
Condensing  engines  should  not  ordinarily  be  used  for  auxiliary 
work. 


390  HYDROELECTRIC  PLANTS. 

The  common  single  valve  engines  have  a  very  limited  range 
of  cut-off  and  cannot  be  depended  upon  to  carry  a  prolonged 
overload  of  more  than  25  per  cent.  If  the  engine  carries  a  heavy 
fly-wheel  a  momentary  over  load  of  from  50  to  75  per  cent,  may 
be  carried. 

On  the  other  hand  the  Corliss  and  other  four  valve  engines  have 
a  very  large  range  of  cut-off  (0  —  £),  and  will  safely  carry  a 
momentary  overload  of  100  per  cent. 

THE    INTERNAL    COMBUSTION    OR    GAS    ENGINE. 

"  The  gas  engine  has  probably  developed  more  slowly  than  any 
other  piece  of  modern  apparatus,  as  it  is  now  30  years  since  the 
Otto  gas  engine  was  introduced.  It  is  only  within  the  last  ten 
years  that  the  larger  type  of  engine,  from  500  to  2,000  h.p.  in 
size,  has  appeared.  The  delay  in  bringing  forward  the  most 
efficient  motive  power  known  is  chiefly  due  to  the  difficulty 
experienced  in  developing  an  efficient  and  inexpensive  method 
of  making  gas.  As  far  as  the  production  of  gas  from  anthracite 
and  non-caking  bituminous  coal  is  concerned  this  problem  has 
apparently  been  solved,  but  it  is  still  in  a  more  or  less  unsolved 
condition  for  the  richer  bituminous  and  semi-bituminous  caking 
coals  of  the  Eastern  States. 

"  The  following  heat  balance  is  believed  to  represent  the  best 
results  obtained  in  Europe  and  the  United  States  up  to  date  in 
the  formation  and  utilization  of  producer  gas 

"Analysis  of  the  average  losses  in  the  conversion  of  one  pound 
of  coal  containing  12,500  B.t.u.  into  electricity: 

B.t.u.  % 

1.  Loss  in  gas  producer  and  auxiliaries 2,500  20 

2.  Loss  in  cooling  water  in  jackets 2,375  19 

3.  Loss  in  exhaust  gases 3,750  30 

4.  Loss  in  engine  friction 813  6.5 

5.  Loss  in  electric  generator 62  0.5 

6.  Total  losses 9,500     76.0 

7.  Converted  into  electrical  energy 3,000     24.0 


12,500  100.0 

:"The  great  objection  to  the  use  of  the  gas  engine  for  electrical 
purposes  has  been:    First,  its  lack  of  uniform  angular  velocity; 


POWER  HOUSE  EQUIPMENT.  391 

secondly,  its  uncertainty  in  action  and  high  cost  of  maintenance; 
and  thirdly,  its  inability  to  carry  heavy  overloads.  Recent 
developments  have  removed  the  first  and  second  objections ;  and 
a  period  of  vigorous  development  has  resulted  in  placing  the  gas 
engine  in  the  front  rank  of  claimants  for  attention  as  a  prime 
mover. 

"The  total  investment  for  a  gas-producer  plant,  all  auxiliaries, 
gas  engines  and  electric  generators,  has  been  reduced  by  the 
elimination  of  the  gas-holding  tank  to  a  point  where  it  is  now 
practically  on  a  par  with  a  first-class  steam  plant  using  high- 
grade  reciprocating  engines. 

"  Where  natural  gas  or  blast-furnace  gas  can  be  obtained,  the 
gas  engine  has  outdistanced  all  competitors ;  and  now  that  some 
of  our  large  manufacturers  have  taken  up  in  earnest  the  problem 
of  designing  producer-gas  plants,  it  is  safe  to  say  that  rapid 
developments  will  result. 

"  The  records  of  operation  of  several  important  installations 
of  gas  engines  in  power  plants  abroad  and  in  this  country  seem 
to  indicate  that  only  one  important  objection  can  be  raised  to 
this  prime  mover,  and  that  is  that  its  range  of  economical  load 
is  practically  limited  to  between  50  per  cent,  load  and  full  load. 
This  lack  of  overload  capacity  is  probably  a  fatal  defect  for  the 
ordinary  power  plant,  more  especially  for  the  average  railroad 
plant  operating  under  a  violently  fluctuating  load,  unless  pro- 
tected by  a  storage-battery  of  comparatively  large  capacity. 

"  Over  a  year  ago,  while  watching  the  effect  of  putting  a  large 
steam  turbine  having  a  sensitive  governor  in  multiple  with 
reciprocating  engine-driven  units  having  sluggish  governors,  it 
occurred  to  the  author  that  here  was  the  solution  of  the  gas- 
engine  problem;  for  the  turbine  immediately  proceeded  to  act 
like  an  ideal  storage-battery;  that  is,  a  storage-battery  whose 
potential  will  not  fall  at  the  moment  of  taking  up  load,  for  all 
the  load  fluctuations  of  the  plant  wrere  taken  up  by  the  steam 
turbine,  and  the  reciprocating  units  went  on  carrying  almost 
constant  load,  while  the  turbine  load  fluctuated  between  0  and 
8,000  kw.  in  periods  of  less  than  10  seconds. 

"  The  combination  of  gas  engines  and  steam  turbines  in  a  single 
plant  offers  possibilities  of  improved  efficiency  while  at  the  same 
time  removing  the  only  valid  objection  to  the  gas  engine. 

"  A  steam-turbine  unit  can  easily  be  designed  to  take  care  of 


392  HYDROELECTRIC  PLANTS. 

100  per  cent,  overload  for  a  few  seconds;  and  as  the  load  fluctu- 
ations in  any  plant  will  probably  not  average  more  than  25  per 
cent,  with  a  maximum  of  50  per  cent,  for  a  few  seconds,  it  would 
seem  that  if  a  plant  were  designed  to  operate  normally  with  50 
per  cent,  of  its  capacity  in  gas  engines  and  50  per  cent,  in  steam 
turbines,  any  fluctuations  of  load  likely  to  arise  in  practice,  could 
be  taken  care  of. 

"  We  have  seen  that  the  thermal  losses  in  the  gas-engine  jacket- 
water  amounted  to  approximately  19  per  cent.,  and  as  the  water 
is  discharged  at  a  temperature  above  100°  it  can  be  used  to 
advantage  for  boiler  feed 

"  The  jacket-water  necessary  for  an  internal  combustion  engine 
will  probably  be  about  40  pounds  per  kilowatt-hour,  assuming 
that  the  jacket-water  enters  at  50°  F.;  then  the  discharge  tem- 


•11  1     -  r\  ^,  .,  __   .n  -.^  ,, 

perature  will  be  oO+  =  109.4°  F." 

4U  X  J.UU 

The  above  is  quoted  from  Mr.  H.  G.  Stott,  and  is  one  of  the 
most  authoritative  and  important  discussions  of  the  gas  engine 
subject  ever  given,  and  marks  the  latest  word  in  that  branch 
of  engineering.  Mr.  Stott  is  in  charge  of  the  largest  steam  power 
plant  in  the  world,  and  being  a  man  of  great  integrity  and  ability, 
he  stands  in  a  prominent  position  to  treat  the  subject  in  a  classic 
manner. 

Therefore,  from  what  he  says  the  gas  engine  producer  plant  is, 
by  far,  the  best  auxiliary  to  install  in  connection  with  a  water 
power  having  large  storage  capacity.  The  water  power  would 
take  the  fluctuating  loads,  leaving  the  steady  average  load  for 
the  gas  engines. 

In  some  cases  the  jacket-water  could  be  used  for  heating, 
though,  as  a  rule,  this  would  be  lost. 

The  gas  engine  is  without  doubt  the  ideal  auxiliary  power. 
There  are  no  boiler  plants  to  depreciate.  The  engine  is  ready  at 
all  times  to  take  up  its  load.  The  modern  gas  engine  is  easily 
started,  has  good  regulation  and  is  as  easily  operated  as  the  steam 
engine.  There  are  many  new  makes  on  the  market,  but  it  is  in 
the  nature  of  an  experiment  when  any  but  the  standard  engine 
is  used.  The  Westinghouse,  Otto&Priestman,  Crosley,  Koerting 
Cockrell  and  Snow  are  among  the  best. 

The  gas  used  may  be  a  mixture  of  gasoline  and  air,  lighting 


POWER  HOUSE  EQUIPMENT.  393 

gas  taken  from  the  city  mains  or  producer  gas.  Usir  j  gasoline, 
the  average  engine  will  consume  J  gallon  of  gasoline  per  effect- 
ive h.p-hr.  Using  city  gas,  the  consumption  will  be  21  to  22 
cubic  feet  of  gas  per  effective  h.p.-hr.  Using  producer  gas  an 
engine  should  develop  one  i.h.p.  per  hr.  with  from  1  to  2  pounds 
good  coal. 

For  plants  of  all  sizes  a  producer  plant  should  be  installed. 
If  the  producer  gas  is  made  directly  from  the  coal,  and  as 
indicated  by  the  above  the  saving  in  coal  is  enormous  The 
price  of  coal  here  again  enters  as  a  factor.  A  gas  engine  producer 
plant  all  complete  with  producer  set  up  and  ready  for  operation, 
would  cost  about  $35  per  brake  h.p.  using  soft  coal,  wood,  etc., 
and  about  $16  for  a  producer  using  hard  coal,  coke,  etc.  These 
figures  do  not  include  the  engine. 

Producer  gas  may  be  made  from  cheap  bituminous  coals, 
anthracite  and  coke.  Usually  small  anthracite  coal  or  coke  is 
used,  but  bituminous  coal,  lignites  and  wood  may  be  employed. 

Tests  show  that  a  16  h.p.  producer  plant  gave  one  horse  power 
for  each  1 . 1  pounds  of  coal,  and  plants  above  50  h.p.  gave  1  h.p. 
for  each  J  pounds  of  coal. 

Gas  engines  without  producers  cost  at  the  factory  as  follows: 
Small  engines  of  from  10  to  30  h.p.  about  $45  per  h.p.  Engines 
up  to  100  h.p.  $40  per  h.p.,  and  above  that  about  $35  per  h.p. 

The  complete  plant  will  cost  about  $85  per  b.h.p. 

ELECTRIC  GENERATORS. 

The  type  of  generator  depends  upon  the  character  of  the  load 
and  the  system  of  distribution.  Therefore  the  various  systems 
of  distribution  will  de  described  in  connection  with  the  gener- 
ators. 

SYSTEMS    OF    DISTRIBUTION. 

Continuous  Current. 

There  are  two  general  systems  of  continuous  current  distribu- 
tion: the  constant  current  and  the  constant  potential  systems. 
The  constant  current  or  series  system  is  seldom  used  in  this 
country  except  for  series  arc  lighting.  The  lamps  take  about 
10  amperes  at  about  50  volts  per  lamp.  The  generator  must 
have  a  voltage  equal  to  50  times  the  number  of  lamps  in  series 
and  a  current  capacity  in  amperes  equal  to  10  times  the  number 
of  series  circuits  in  parallel. 


394  HYDROELECTRIC  PLANTS. 

Knowing  the  number  of  arcs  to  be  supplied  for  city  lighting, 
and  those  for  commercial  lighting,  the  peak  load  can  be  decided 
on.  Arc  machines  will  carry '25  per  cent,  overload  for  a  half 
hour,  and  their  capacity  need  therefore  only  be  75  per  cent,  of 
the  peak  load. 

™<       .      ...       ..     .,    -  «      (Voltage  of  the  machine) 

The  size  being  limited  by  - — ^-^ j— r—         —  =  to  about 

Voltage  of  the  lamp 

75  kw  or  less,  the  generator  will  be  of  the  belted  type. 

It  should  rest  on  a  heavy  timber  frame  well  oiled,  and  bolted 
with  deeply  countersunk  bolts  so  as  to  well  insulate  it  from  the 
ground.  The  load  is  generally  quite  constant,  and  cheap  gov- 
ernors may  be  employed  for  regulation. 

The  constant  potential  or  parallel  system  is  in  almost  universal 
use  in  this  country.  In  this  system  the  current  capacity  in 
amperes  is  equal  to  the  current  capacity  of  the  lamp  used  times 
the  number  of  lamps  in  multiple.  There  are  three  general 
methods  of  wiring,  namely ;  the  two-wire  method  for  lamps  and 
small  motors  (110  volts);  the  three-wire  method,  lamps  and 
motors  (220  to  440  volts)  and  the  five-wire  method  for  lamps  and 
motors  (440  volts). 

Sharp  peaks  are  sure  to  occur  and  the  safe  overload  capacity 
of  the  generators  must  be  at  least  three  times  the  average  load. 

First  class  governing  is  an  essential  feature  in  the  successful 
operation  of  this  system. 

The  best  practice  is  to  have  two  machines,  each  being  of 
sufficient  size  to  carry  the  entire  probable  load  as  an  overload 
of  25  per  cent. 

The  machines  may,  and  usually  are,  operated  in  parallel. 

No  precautions  are  necessary  to  insulate  the  frame  from  the 
ground. 

Alternating  Current. 

In  alternating  systems  there  are  two  general  classes,  the  single 
phase  and  the  polyphase. 

The  single  phase  system  may  be  high  tension  at  the  generator 
and  stepped  down  at  the  load,  or  may  be  stepped  up  to  very 
high  tension  at  the  generator  and  stepped  down  at  the  load. 

The  former  has  only  one  set  of  transformers,  those  for  stepping 
down  the  voltage  from  1000  to  5000  volts  to  50,  100  or  200  volts. 
The  secondary  may  be  two  or  three-wire. 


POWER  HOUSE  EQUIPMENT: 


395 


The  latter  has  two  sets  of  transformers,  one  for  stepping  up 
and  one  for  stepping  down.  The  transmission  voltage  may  be 
from  5000  to  60,600  volts. 

The  advent  of  a  single-phase  motor  has  brought  the  single- 
phase  system  into  great  prominence,  since,  aside  from  the  added 
cost  in  long  transmissions,  it  possesses  the  following  advantages 


>  M  >/Ss 


liRTT 


Unrr 


FIG.  378. 

over  the  polyphase  systems:  By  using  single-phase  a  saving  of 
10  to  40  per  cent,  of  the  first  cost  of  the  motor  transformer  instal- 
lation is  affected;  fewer  transformers  are  required  with  a  conse- 
quent saving  in  transmission  losses  of  10  to  20  per  cent.  Fewer 
meters  are  required,  which  is  a  good  saving,  as  each  small  meter 
consumes  about  1  per  cent,  of  the  power  measured ;  also  the  labor 


8== 


FIG.  379. 


of  installing  each  of  the  numerous  meters  is  materially  lessened ; 
it  costs  less  to  erect  the  pole  line,  etc. 

The  above  are  very  important  facts  and  should  be  well  con- 
sidered. 

The  working  voltage  may  be  100,  120,  200,  or  240  volts. 

One  of  the  most  common  two-wire  systems  is  that  shown  in 
Fig.  378,  the  two  generators  and  the  lamps  being  in  parallel. 


396 


HYDROELECTRIC  PLANTS. 


Two  hundred  and  twenty-volt  lamps  are  now  used  to  some 
extent,  in  which  case  the  distribution  is  materially  cheapened. 

In  the  three-wire  system  (Fig.  379)  the  transformers  T  are  of 
large  size,  supplying  a  long  line  of  lamps  or  small  motors. 

Either  of  the  transformer  connections  shown  may  be  used, 
care  being  taken  to  connect  unlike  terminals  at  P. 

The  polyphase  system  may  be  divided  into  the  two-phase  and 
the  three-phase. 

The  two-phase,  four- wire  system,  shown  in  Fig.  380,  consists 
of  two  single-phase  circuits  differing  in  phase  by  90°. 

The  chief  advantage  claimed  for  this  system  is  that  a  rotating 
field  may  be  established,  which  permits  the  use  of  two-phase 


FIG.  380. 

induction  motors  and  the  self-starting  of  synchronous  motors. 
The  two-phase  induction  motors  will  start  up  under  full  load,  but 
the  synchronous  motors  will  not,  being  run  up  to  speed  unloaded. 
The  success  of  the  single-phase  motor,  of  course,  lessens  these 
advantages  so  that  the  single-phase  should  be  considered  the 
better  system  up  to  30  h.p. 

Street  railways  have  frequently  been  operated  from  this  system 
synchronous  converters  supplying  the  continuous  current.     For 
long  transmissions  step  up  and  step  down  transformers  would 
be  used. 

This  system  requires  the  same  amount  of  copper  as  the  single- 
phase. 

The  three-phase  system  shown  in  Fig.  381  is  by  far  the  most 


POWER  HOUSE  EQUIPMENT. 


397 


important  alternating  current  system  in  use  to-day.  Especially 
is  this  true  when  considered  in  connection  with  hydro-electric 
power  plants.  By  it  power  is  being  successfully  transmitted  at 
a  pressure  of  60,000  volts  for  distances  as  high  as  150  miles. 
As  shown  above,  no  step  up  transformers  are  used,  though,  of 
course,  for  higher  voltages  than  10,000,  and  preferably  voltages 
above  4300,  the  voltage  is  stepped  up  for  transmission  and  then 
stepped  down  for  use. 

In  comparing  the  actual  operation  of  two-phase  and  three- 
phase  systems  there  is  little  to  choose  between  them.  The  three- 
phase  saves  25  per  cent,  in  copper  over  the  single  and  two-phase 
systems  on  the  transmission. 


FIG.  381. 

The  selection  of  the  proper  size  for  the  generators  is  one  of 
the  very  important  problems,  and  while  an  easy  one,  it  is  usually 
the  cause  for  the  most  inexcusable  mistakes. 

At  Constantine,  Mich.,  there  is  a  modern  hydro-electric  power 
plant  built  by  a  Chicago  company.  They  have  two  600  kw. 
generators  having  a  maximum  capacity  (allowing  for  50  per  cent, 
overload,)  of  2460  h.p.  To  drive  these  generators  they  have 
turbines  with  a  maximum  capacity,  allowing  for  loss  in  gearing, 
of  1700  h.p. 

This,  too,  is  for  the  maximum  working  head  of  11  feet.  Fre- 
quently the  head  is  reduced  by  back  water  to  6  feet,  in  which 
case  they  can  hardly  carry  their  small  lighting  load,  though  at 
the  same  time  thousands  of  horse  power  are  passing  over  the  dam 
and  going  to  waste. 


398  HYDROELECTRIC  PLANTS. 

This  is  not  an  extreme  case,  but  one  much  better  than  is  often 
found. 

Generators  are  rated  at  a  unity  power  factor.  Therefore  if 
the  power  factor  is  .80  the  generator  will  have  only  about  .80  of 
its  rated  capacity. 

While  electrical  manufacturers  do  not  guarantee  it,  yet  it  is 
a  fact  that  any  of  the  standard  generators  will  carry  a  25  per  cent, 
overload  right  along  and  a  50  per  cent,  overload  for  two  or  three 
hours  without  doing  them  any  injury. 

Exciters  for  these  generators  should,  in  all  cases,  be  belted 
to  the  shaft  to  give  the  most  uniform  velocity.  Where  the  head 
fluctuates  it  is  bad  engineering  to  drive  the  exciter  with  one 
turbine,  the  speed  of  which  cannot  be  controlled.  The  generator 
line  shaft,  when  the  plant  is  properly  designed,  is  the  best  to 
drive  the  exciter  from.  In  the  case  of  horizontal  turbines  and 
direct  connection  it  is  very  difficult  to  keep  up  the  speed. 

The  latest  method  is  to  drive  one  exciter  with  a  motor. 

The  loss  of  speed  through  diminished  head  reduces  the  voltage 
of  the  line  current  and  also  reduces  the  frequency.  Where  lamps 
are  operated  or  where  the  hydraulic  plant  is  operated  in  connec- 
tion with  some  distant  steam  plant  this  reduction  of  the  frequency 
is  a  very  serious  thing.  The  lamps  refuse  to  work  and  the  distant 
generators  will  not  run  in  parallel. 

A  variation  of  2  per  cent,  from  the  normal  frequency  may 
seriously  affect  the  operation  of  the  plant. 

To  get  the  proper  size  of  generator,  first  find  the  greatest  peak 
loads  which  are  apt  to  occur.  Divide  this  peak  load  by  1.5; 
this  will  give  the  rated  capacity  of  the  generator  for  a  unity 
power  factor.  Now  if  the  load  is  an  inductive  one  and  the 
power  factor  is  .80  multiply,  the  rated  capacity  as  found  from 
the  above,  by  1.2.  This  gives  the  commercial  rating  of  the 
generator. 

The  exciter  capacity  should  be  about  30  per  cent,  greater  for 
an  .80  power  factor  than  for  a  unity  power  factor.  The  exciter 
capacity  for  an  .80  power  factor  should  be  about  4  per  cent,  of 
the  generator  capacity,  as  found  from  the  above. 

SWITCH  BOARDS. 

The  switch  board  is  the  most  variable  factor  in  the  design 
of  the  power  house  and  one  of  the  least  understood.  Everything 


POWER  HOUSE  EQUIPMENT. 


399 


about  the  switch  board  should  be  thoroughly  made  and  of  the 
best  materials.  Marbelized  slate  for  boards  up  to  600  volts  is 
a  good  substitute  for  marble,  the  chief  objection  being  that  it 
scratches  easily. 

Whether  of  slate  or  marble  care  should  be  exercised  in  select- 
ing slabs  free  from  mineral  veins.  White  Italian  marble  IJ-inch 
to  2-inch  thick  is,  in  the  long  run,  the  most  satisfactory.  The 
Standard  Marble  Company  of  Cincinnati,  O.,  sell  a  very  good 
grade  of  marble.  One  and  a  quarter-inch  costs  about  65  cents, 
IJ-inch  costs  about  80  cents,  and  If  to  2-inch  costs  about  $1.10 
per  square  foot. 

The  frame  is  in  almost  all  cases  made  of  angle  irons  as  shown 
in  Fig.  382,  though  especially  prepared  wood  boiled  in  paraffin 


FIG.  382. 

or  linseed  oil  has  been  used  for  high  tension  work.  A  1J  to 
2-inch  angle  iron  is  plenty  large  for  the  ordinary  board.  Fancy 
heads  are  used  on  the  face  side  of  the  board.  The  iron  work 
must  be  painted  before  setting  up.  Felt  washers  are  used 
between  the  iron  and  marble.  The  holes  c  are  for  fastening  the 
various  panels  together. 

There  is  no  good  reason  why  the  engineer  should  not  make  the 
complete  switch  board  on  the  site,  and  it  is  certainly  a  good  plan 
for  him  to  select  the  instruments  with  great  care. 

For  eight  or  ten  dollars  a  drill  press,  such  as  is  used  by  black- 
smiths, can  be  purchased  with  which  to  drill  holes  in  the 
marble.  It  should  be  attached  to  a  plank  A,  as  shown  in  Fig. 


400 


HYDROELECTRIC  PLANTS. 


383,  and  should  be  driven  with  a  1  h.p.  motor  The  drill  should 
have  a  speed  of  about  170  r.p.m.,  a  table  on  which  to  lay  the 
slab  is  very  handy,  though  of  course  the  floor  (if  perfectly  level) 
will  serve  the  purpose.  It  would  take  about  one  day  to  bore  the 
holes  for  the  board  shown  in  Fig.  382. 

The  ordinary  twist  drill  is  used,  plenty  of  water  being  fed  to 
the  cutting  edge.  Holes  up  to  7-16-inch  may  be  drilled  in  one 
drilling;  up  to  J-inch  use  two  drills,  and  from  that  to  IJ-inch, 
use  three  different  sizes.  If  the  holes  are  not  true  file  them  with 
a  rat-tail  file. 

To  lay  out  the  holes  for  drilling  use  an  indelible  pencil  and 
prick  punch.  Where  the  drill  has  chipped  the  marble  at  back  of 


FIG.  383. 

board  fill  out  with  plaster  of  Paris.  When  the  individual  panels 
are  completed  they  are  bolted  together  with  f-inch  bolts  and 
temporarily  stood  up  while  the  bus  work  is  done.  The  back  of 
a  switch  board  is  where  the  workman's  skill  is  shown.  In  bus 
work  use  what  is  known  as  half  hard  copper  bar.  This  may  be 
had  of  the  Detroit  Copper  &  Brass  Rolling  Mills,  Detroit,  Mich. 
A  bar  thicker  than  7-16-inch  is  very  difficult  to  bend. 

Aluminum  makes  excellent  bus-bars,  as  it  has  a  large  area  to 
dissipate  heat  and  is  light  in  weight.  All  connections  to  it  have 
to  be  bolted. 

One  thousand  amperes  per  square  inch  of  copper  and  750 
amperes  per  square  inch  of  aluminum  is  common  practice  for 
switches  and  bus-bars.  All  copper  parts  carrying  currents  of 


POWER  HOUSE  EQUIPMENT. 


401 


opposite  polarity  must  have  a  certain  amount  of  air  space  be- 
tween, as  given  in  the  table  XLIX.  This  table  may  be  used  for 
either  alternating  or  continuous  current. 

Due  allowance  must  be  made  for  the  conditions  at  the  board 
during  operation,  and  if  the  atmosphere  will  be  damp  a  wider 
arcing  distance  must  be  allowed. 

TABLE  XLIX. 
SPACING  OF  Bus  BARS  AND  SWITCH  BLADES. 


Voltage  volts. 

Current  amperes. 

Distance  between  nearest  metal 
parts,  inches. 

0  to  125 

0  to  10 
10  to  25 
25  to  50 

0.75 
1.00 
1.25 

125  to  250 

0  to  10 
10  to  35 
35  to  100 
100  to  300 
300  to  1000 

1.50 
1.75 
2.25 
2.50 
3.00 

250  to  600 

Oto  10 
10  to  35 
35  to  100 

3.50 
4.00 
4.50 

600  to  1000 

Oto  10 
100 

5.00 
7.00 

Fig.  384  represents  a  simple  bus-bar  for  boards  of  moderate 
size. 

On  very  heavy  bus-bar  work  instead  of  bending  the  bars, 
t':ey  are  attached  as  shown  in  Fig.  385. 

Care  must  be  taken  to  maintain  the  proper  arcing  distance 
from  the  steel  frame  of  the  board.  The  flexible  connecting 


FIG.  384. 

cables  are  soldered  into  the  lugs  as  shown  in  Fig.  386  at  a,  but  all 
strip  connections  as  c,  are  bolted  to  the  bus-bars  with  from  one 
to  four  bolts. 

Where  the  bus-bars  are  over  T\  inch  thick  it  is  well  to  make 
them  of  two  or  more  strips  with  air  spaces  between  for  ventila- 
tion. A  contact  surface  of  one  square  inch  per  100  amperes 
should  be  allowed  at  joints. 


402 


HYDROELECTRIC  PLANTS. 


For  heavy  alternating  currents  the  bus-bars  may  be  m^de 
of  tubing  to  keep  down  the  losses  due  to  skin  effect. 

In  high  tension  work  (6000  or  more  volts)  the  bus-bars  are 
not  usually  placed  on  the  board,  but  mounted  on  porcelain 
insulators  behind  it. 

Where  the  boards  are  of  such  large  size  that  a  single  attendant 
can  not  operate  them  the  heavy  switches  are  operated  from  a 
control  board.  Each  switch  is  operated  by  an  electric,  pneu- 
matic or  hydraulic  motor,  which  is  put  in  motion  from  a  small 
board  representing  on  a  small  scale  the  large  one.  All  the 
measuring  instruments  are  mounted  on  the  control  board:  fine 
wires  connect  them  to  the  large  bus-bars  on  the  main  board. 


FIG.  385. 


FIG.  386. 


In  an  alternating  current  plant  the  current  for  operating  the 
large  switches  is  derived  from  a  motor-generator  in  connection 
with  a  storage  battery.  Where  the  hydraulic  head  is  sufficient, 
hydraulic  pistons  may  be  used,  the  valves  being  actuated  by 
electro  magnets. 

SWITCHES  AND  INSTRUMENTS. 

Each  switch  is  proportioned  to  the  current  and  voltage.  The 
higher  pressures  broaden  and  complicate  them,  while  the  heavy 
currents  make  the  switch  heavy  and  bulky.  They  may  consist 
of  one  or  more  blades  and  are  designated  by  letters  which  indi- 
cate the  type  of  instrument  as  follows:  S.P.S.T.  means  single 
pole  (one  blade),  single  throw  (handle  of  switch  in  Fig.  386  does 
not  open  more  than  90°).  D.P.D.T.  means  double  pole  and 
double  throw,  as  in  Fig.  387,  etc.  Then  the  switches  may  or 
may  not  have  fuses  as  in  Fig.  388. 


POWER  HOUSE  EQUIPMENT.  403 

All  contact  surfaces  must  be  so  proportioned  as  to  carry  but 
50  amperes  per  square  inch  of  surface.  These  contacts  should 
at  full  load  not  heat  to  more  than  50  degrees  Fahrenheit  above 
the  atmosphere. 

A  standard  size  for  switch  board  panels  is  62x30x2  inches  for 
the  main  upper  part,  with  a  sub-base  28x30x2  inches. 

In  polyphase  work,  where  there  are  several  units,  the  usual 
practice  is  to  have  one  panel  for  each  generator  and  one  panel 
for  each  exciter.  The  generator  panel  has  the  ammeter,  volt 
meters,  generator  switches,  fuses,  field  switch  fuses,  pilot  lamp 
for  generator,  and  on  the  back  of  the  panel  a  lightning  arrester 
for  each  phase,  a  station  transformer  and  a  ground  detector. 

Table  XLIX  gives  the  proper  spacing  distances  for  the  me- 
tallic parts.  Only  in  very  small  switches  of  high  voltage  should 
the- hinge  a,  Fig.  388,  be  made  to  carry  the  current. 


FIG.  388. 

For  switch  board  work  the  switches  have  lugs  of  sufficient 
length  to  project  through  the  board  and  receive  the  strips, 
washer  and  nuts. 

For  higher  tension  switches  of  from  600  to  10,000  volts  a  bar- 
rier of  marble,  slate  or  glass  is  inserted  between  the  poles  or 
blades  of  the  switch  to  prevent  arcing,  as  in  Fig.  389.  This  is 
really  a  single  throw  switch  with  one  added  contact  making  it 
a  double  throw  suited  for  as  high  as  20,000  volts,  though  for 
tensions  of  from  6,000  to  20,000  volts  an  oil  switch  is  considered 
the  best. 

Fig.  390  shows  a  high  tension  switch  in  which  A  is  a  copper 
piston  and  C  a  lever  on  the  front  of  the  board  by  which  the  eight 
pistons  are  brought  into  contact  with  the  eight  contacts  B. 
The  eight  cylinders  D  are  of  porcelain  and  divided  into  pairs, 


404 


HYDROELECTRIC  PLANTS. 


each  pair  having  a  connection  for  a  ;vire  from  the  generator  and 
one  to  the  line.  The  eight  tubes  therefore  take  care  of  four 
circuits. 

Actual  practice  has  demonstrated  the  oil  switch  to  be  the  best, 
especially  for  inductive  loads,  and  most  compact  for  voltages 
up  to  10,000,  while  for  voltages  above  this  a  long  break  switch,  is 
considered  the  most  reliable,  dependance  being  placed  on  the 
length  of  break  alone,  which  for  6,600  volts  is  30  inches,  for 
22,000  volts  6  feet. 


FIG.  389. 


FIG.  390. 


It  is  necessary  to  know  the  voltage  of  all  machines  connected 
to  the  board  and  also  the  voltage  on  the  out-going  feeders.  The 
best,  and  what  has  become  the  standard  voltmeter  for  direct 
currents  is  the  Weston.  It  is  mounted  on  the  front  of  the  board 
and  a  lamp  provided  to  light  the  dial.  All  voltmeters  must  be 
dead  beat  and  accurate  to  within  1  per  cent,  at  all  loads.  It  is 
quite  essential  to  have  at  least  two  voltmeters  so  that  one  may 
be  used  as  a  check  on  the  other,  but  it  is  not  necessary  to  have 
one  for  each  machine  and  feeder,  as  a  multi-contact  switch  may 
be  used  to  connect  them  with  any  circuit  it  is  wished  to  get  the 
voltage  of.  (See  Fig.  391.) 

For  alternating  currents  it  is  customary  to  connect  the  volt- 
meters through  a  transformer,  so  as  not  tc  submit  the  instru- 


POWER  HOUSE  EQUIPMENT.  405 

ment  to  the  high  tension.  These  potential  transformers  are 
attached  to  the  back  of  the  board,  or  placed  on  the  wall.  They 
are  very  small  transformers  and  should  not  carry  any  other  load 
than  the  voltmeter. 

Voltmeters  are  often  mounted  on  swinging  brackets  at  the 
ends  of  the  board. 

The  range  of  all  voltmeters  should  be  about  50  per  cent,  above 
normal  load. 

For  voltages  of  10,000  and  more  an  electrostatic  voltmeter 
is  often  used.  It  may  be  connected  in  parallel  across  high  ten- 
sion lines  without  the  use  of  a  transformer. 

Some  voltmeters  are  so  designed  as  to  work  on  either  alter- 
nating or  continuous  current. 


FIG.  391. 

A  voltmeter  switch  which  is  largely  in  use  is  shown  in  Fig.  391. 
By  plugging  in  between  a  and  b  and  a'  6',  any  of  the  generators 
or  feeders  can  be  connected  to  the  instrument. 

One  of  the  feeder  lines  in  Fig.  391  could  be  replaced  by  pilot 
wires  run  back  to  the  center  of  distribution.  Then  by  con- 
necting with  the  voltmeter  the  pressure  at  the  far  end  of  the 
line  could  be  read.  This  method  is  only  adapted  for  lines  under 
two  or  three  miles  in  length.  A  better  way  is  to  use  a  compensa- 
tor. 

This  is  a  device  by  which  the  voltmeter  Dreading  is  decreased 
by  an  amount  equal  to  the  drop  in  the  line.  The  Westinghouse 
Mershon  type  is  one  of  the  best. 

The  connections  for  the  Mershon  compensator  are  given  in 


406 


HYDROELECTRIC  PLANTS. 


Fig.  392.  A  is  an  ordinary  potential  transformer,  B  is  an  induc- 
tance and  C  a  non-inductive  resistance,  and  D  and  E  are  small 
transformers.  This  is  the  most  common  arrangement  and  is 
suitable  for  the  most  inductive  loads,  such  as  motors  or  motors 


FIG.  392. 

and  lamps.  For  a  small  village  lighting  plant  it  is  not  thought 
necessary  to  use  any  such  device  as  the  telephone  may  be  relied 
on  to  give  warning  of  any  dissatisfaction  on  the  part  ot  the  cus- 
tomers. 


FIG.  393. 

The  Westinghouse  Company  manufactures  a  compensator 
suitable  for  lines  having  little  self-induction,  such  as  incandescent 
lighting.  The  connections  are  as  in  Fig.  393;  /  is  the  ordinary 
potential  transformer.  The  voltmeter  V  is  of  the  coil  and 


POWER  HOUSE  EQUIPMENT.  407 

plunger  type.  When  the  voltage  at  the  distributing  end  is  correct 
the  hand  of  the  voltmeter  is  at  0.  The  adjustment  is  obtained 
by  plugging  in  along  a,  and  by  rotating  the  contact  c. 

The  Weston  ammeter  is  the  most  widely  used,  whether  direct 
or  alternating,  and  is  accurate  to  within  1  per  cent,  at  all  loads, 
and  is  also  dead  beat;  that  is,  the  oscillations  soon  cease  after 
a  change  of  load. 

Usually,  where  the  current  is  moderate,  say  less  than  250  am- 
peres, and  the  voltage  not  above  5,000,  alternating  current 
ammeters  are  connected  directly  in  the  main  circuit,  as  in  Fig. 
394,  but  for  high  voltages  and  large  currents  a  current  trans- 
former is  connected  as  shown  in  Fig.  395. 

A  recording  ammeter,  whether  for  continuous  or  alternating 
current,  should  be  part  of  every  switch  board  equipment  in  order 
that  the  peak  may  be  studied  and  due  charges  made.  The 
Bristol  Company  of  Waterbury,  Conn.,  make  both  recording 
ammeters  and  voltmeters. 


-©• 


0 


FIG.  394.  FIG.  395. 

There  should  be  an  ammeter  in  each  phase  and  one  for  the 
field  exciting  connections  in  addition  to  the  watt-hour  meters. 

The  circuit-breaker  is  the  safety  valve  of  a  switchboard. 
Its  purpose  is  to  open  the  circuit  at  times  of  short  circuit  and 
overloads.  It  commonly  consists  of  a  solenoid  which  operates 
a  trigger,  releasing  the  switch  when  the  current  exceeds  a  certain 
predetermined  amount.  These  instruments  are  quite  expen- 
sive and  may  be  considered  as  a  luxury  in  view  of  the  fact  that 
the  ordinary  fuses  can  be  relied  on  to  a  certain  extent.  How- 
ever, it  is  an  excellent  plan  to  equip  each  generator  and  each 
feeder  with  a  single -pole  circuit-breaker. 

Circuit-breakers  serve  to  protect  against  lightning,  though 
they  should  not  be  relied  on  for  this  purpose.  They  may  also 
take  the  place  of  a  switch.  A  great  advantage  possessed  by 
circuit-breakers  over  fuses  is  the  ease  and  quickness  with  which 
the  broken  circuit  may  again  be  put  in  operation.  They  are 


408  HYDROELECTRIC  PLANTS. 

also  much  more  accurate  than  a  fuse.  The  circuit-breakers 
should  be  so  constructed  that  the  main  line  breaker  will  act 
somewhat  behind  the  branch  line  breaker,  otherwise  the  main 
breaker  may  operate  at  the  same  time  the  branch  opens,  thus 
needlessly  interrupting  the  service. 

The  contacts  should  be  of  carbon  and  the  breaker  should  be 
able  to  carry  a  75  per  cent,  overload.  They  may  be  had  of  as 
many  poles  as  desired. 

A  good  plan  is  to  have  a  circuit-breaker  on  each  side  of  the 
circuit,  in  which  case  one  side  will  open  automatically  if  it  is 
attempted  to  close  the  other,  while  the  short  remains.  If  a  single- 
pole  breaker  is  used  connecting  the  generator  to  the  board  it  is 
best  practice  to  place  it  on  the  negative  side.  There  are  circuit- 
breakers  which  open  the  circuit  for  both  too  high  and  too  low 
currents.  These  are  used  in  connecting  generators  to  storage 
batteries. 

Circuit-breakers  are  not  quite  so  common  on  alternating 
current  boards  as  they  are  on  continuous  current  boards,  but 
for  high-tension  transmission  work  they  should  certainly  be 
used.  When  there  is  any  uncertainty  about  the  generators 
keeping  in  step,  as  in  the  case  where  turbines  have  no  governors, 
it  is  advisable  to  connect  them  to  the  board  through  a  breaker. 

After  years  of  experience  with  the  Niagara  transmission  to 
Buffalo,  a  circuit-breaking  switch  has  recently  been  installed  on 
each  phase  of  the  outgoing  feeders.  Thus  three  three-phase 
transmission  lines  have  nine  breakers.  The  voltage  is  22,000 
and  it  was  found  that  the  break  of  the  switch  had  to  be  fully 
six  feet.  The  best  type  for  high  tension  work  is  undoubtedly 
the  oil  circuit-breaker.  In  this  type  the  break  may  be  much 
shorter,  as  the  oil  quenches  the  arc. 

Many  boards  have  one  oil  circuit-breaker  on  each  feeder 
panel,  thereby  protecting  the  board  from  overloads  and  shorts 
on  the  transmission  line,  but  leaving  the  generators  and  exciters 
to  the  care  of  fuses. 

Fuses  form  the  most  common  method  of  providing  an  auto- 
matic interruption  of  the  circuit  during  overloads  and  shorts. 
It  is  to  their  cheapness  that  they  owe  their  popularity,  for  they 
are  the  most  unsatisfactory  part  of  a  board's  equipment.  De- 
pending on  the  fusing  point  of  a  metal,  they  are  not  at  all 
accurate. 


POWER  HOUSE  EQUIPMENT.  409 

A  common  way  is  to  have  the  fuses  a  part  of  the  switch  for 
low-tension  work,  but  for  high-tension  boards  it  is  advisable  to 
have  the  fuses  on  the  back  of  the  board. 

In  Fig.  396  a  General  Electric  fuse  box  is  shown.  The  entire 
box  may  be  pulled  off  the  board,  the  slips  c  being  only  in  fric- 
tional  contact  with  the  terminals  t.  These  fuses  are  made  for 
as  high  as  150  amperes  and  2,500  volts.  For  higher  tension 
boards  the  fuse  blocks  are  placed  at  back  of  board  and  the  blocks 
removed  by  means  of  an  insulated  pole  some  three  or  four  feet 
in  length  to  protect  the  operator  from  shocks. 

All  fuses  should  be  enclosed,  and  a  common  form  is  enclosed 
in  a  fiber  or  hard  rubber  tube.  On  alternating  current  switch 
boards  the  practice  seems  to  be  to  eliminate  fuses  as  much  as 
possible,  though  it  is  still  common  to  place  fuses  on  the  feeders. 

The  wattmeter  is  to  the  power  station  what  the  journal  and  ledger 
are  to  the  successful  business  man.     In  order  to  improve  or 


FIG.  396. 

maintain  the  efficiency  of  the  plant  one  should  know  the  amount 
of  power  being  sent  out  by  each  machine  and  by  each  feeder. 

These  instruments  are  usually  mounted  on  the  board,  though 
if  the  board  is  crowded  or  for  any  other  reason,  they  may  be 
placed  near  the  generator. 

The  power  on  a  continuous  current  line  may  be  obtained  at 
any  time  by  taking  the  product  of  the  voltmeter  and  ammeter 
readings  at  the  same  instant,  thus  getting  the  power  in  watts, 
from  which  the  horse  power  is  obtained  by  dividing  by  746  or 
the  kilowatts  by  dividing  by  1000. 

The  wattmeter,  however,  indicates  this  product  so  that  the 
watts  may  be  read  off  directly  by  simply  pushing  a  button. 

However,  it  is  usually  desirable  to  keep  a  record  of  the  watt- 
hours,  as  the  watt-hour  is  the  unit  on  which  the  charge  for  power 
is  based. 

To  get  this  continuous  all-day  record  the  watt-hour  meter 


410 


HYDROELECTRIC  PLANTS. 


is  used.  The  best  known  instrument  for  this  purpose  is  the 
Thomson,  which  may  be  used  with  either  alternating  or  con- 
tinuous current.  In  this  instrument  there  are  a  number  of  dials 
at  the  top  from  which  the  total  watt-hours  may  be  read  like  the 
readings  on  a  gas  meter. 

Fig.  397  shows  a  Thomson  watt-hour  meter  connected  to  a 
two  wire  line. 


FIG.  397. 

The  power  in  alternating  current  circuits  is  equal  to  the  pro- 
duct of  the  current  and  the  in  phase  component  of  the  e.m.f., 
and  is  obtained  directly  by  connecting  a  wattmeter  in  each 
separate  phase.  In  single-phase  circuits  the  connections  are 
precisely  the  same  as  in  continuous  current  circuits.  In  un- 


FIG.  398. 

balanced  two-phase  circuits  there  should  be  a  wattmeter  in  each 
phase.  The  total  power  equals  the  sum  of  the  two  readings, 
but  in  balanced  two-phase  circuits,  such  as  motor  load,  there 
need  be  only  one  meter,  and  its  reading,  multiplied  by  two,  will 
give  the  total  power.  In  three-phase  circuits  only  two  meters 
are  necessary,  connected  as  shown  in  Fig.  398.  The  total  power 


POWER  HOUSE  EQUIPMENT. 


411 


is  equal  to  the  sum  of  the  readings.  The  energy,  which  is  equal 
to  the  product  of  the  power  and  the  time,  is  obtained  with  a 
watt-hour  meter.  For  single-phase  circuits  the  connections  are 
the  same  as  for  continuous  current  circuits. 

In  two-phase  circuits  there  should  be  two  instruments  if  the 
load  is  unbalanced  and  one  if  balanced.  The  connection  is  the 
same  as  for  single -phase,  and  the  total  energy  is  equal  to  the  sum 
of  the  two  readings,  or  twice  the  reading  in  one  phase. 

In  three-phase,  star-connected  loads,  one  meter  will  measure 
one  third  the  energy;  in  some  cases  the  meter  may  be  connected 


FIG.  399. 

with  an  artificial  neutral,  as  shown  in  Fig.  399.  In  unbalanced 
three-phase  circuits  two  instruments  connected  as  shown  in  Fig. 
400  should  be  used. 

Where  the  pressure  is  over  550  and  under  3,000  volts  it  is  not 
thought  advisable  to  pass  the  line  voltage  directly  through  the 
instrument,  so  small  transformers  (t)  are  used,  as  in  Fig.  401. 

Induction  watt-hour  meters  are  sometimes  used.  These  are  for 
alternating  currents  only,  and  have  to  be  adjusted  to  the  par- 
ticular frequency  of  the  line.  They,  however,  have  no  com- 
mutator to  get  out  of  order. 

For  series  arc  lighting  the  Thomson  meter  is  connected  as 


412 


HYDROELECTRIC  PLANTS. 


in  Fig.  402,  a  cut  out,  a,  being  provided  to  short  circuit  the  line 
in  case  of  an  open  circuit  beyond. 

In  the  case  of  very  heavy  currents  a  special  meter  is  used, 
shown  in  Fig.  403. 


FIG.  400. 

All  meters  should  be  accurate  to  within  3  per  cent.  They 
should  maintain  this  accuracy  throughout  the  load  and  be  of 
sufficient  size  to  carry  the  peak  loads. 

They  should  not  waste  more  than  1  per  cent,  of  the  energy 
delivered  to  them. 


FIG.  401. 


FIG.  402. 


The  drop  in  voltage  caused  by  its  presence  in  the  circuit  should 
not  exceed  0.25  per  cent. 

It  often  becomes  advisable  to  charge  two  rates,  one  for  the 
short  heavy  peak  loads,  and  another  for  the  more  steady  average 


POWER  HOUSE  EQUIPMENT. 


413 


loads.  For  measuring  this  kind  of  a  load  a  two  rate  meter  is 
used.  This  instrument  will  record  the  two  periods  of  load  sepa- 
rately, thus  allowing  the  desired  rates  to  be  changed. 

There  are  meters  which  record  the  ampere-hours  instead  of 
watt-hours,  but  these  are  not  to  be  recommended  for  power 
house  work. 


FIG.  403. 

LIGHTNING  ARRESTERS. 

White  some  arresters  work  equally  well  on  direct  and  alter- 
nating current  circuits,  the  greater  number  do  not.  A  very  reli- 
able arrester  is  the  Garton,  which  is  shown  in  Fig.  404. 

The  Westinghouse  arrester  is  largely  used  on  direct-current 
circuits  up  to  700  volts. 


FIG.  404. 


FIG.  405. 


r~  The  General  Electric  Company  puts  out  a  magnetic  blow-out 
arrester  which  has  been  largely  used,  especially  on  electric  rail- 
way lines,  etc.,  connections  are  shown  in  Fig.  405.  These 
arresters  are  made  for  voltages  up  to  850.  There  should  be  one 
on  each  side  of  the  line  for  added  safety. 


414 


HYDROELECTRIC  PLANTS. 


For  alternating  current  practice  the  only  satisfactory  arresters 
are  those  using  a  series  of  cylinders,  discs  or  spheres,  having 
small  air  gaps  between  them  and  connected  in  series,  the  number 
depending  on  the  voltage  of  the  system. 

The   Wurts   arrester,   made   by   the    Westinghouse,   and   the 


FIG.  406. 

General  Electric  arresters  are  representative  of  this  class.  They 
are  made  for  1,000  volts,  and  when  a  line  of  higher  voltage  is  to 
be  protected  enough  are  placed  in  series  to  sum  up  the  required 
voltage,  as  in  Fig.  406. 


To  Switchboard 


-@ 


ToSwitchboarct 

FIG.  407. 

The  General  Electric  arrester,  shown  in  Fig  407,  is  installed 
for  10,000  volts.  The  choke  coil  for  arresters  may  be  made  by 
coiling  up  about  150  feet  of  the  line  wire, .making  a  coil, about 
15  inches  in  diameter.  The  ground  indicated  in  the  figures  by 
••  must  be  very  carefully  made.  A  steel  penstock  or  head 


POWER  HOUSE  EQUIPMENT. 


415 


rack  makes  a  good  ground,  or  a  galvanized  iron  pipe  driven 
12  or  14  feet  Into  moist  earth  makes  a  good  ground.  All  con- 
nections must  be  made  as  directly  as  possible  and  of  ample  size 
to  carry  the  whole  current. 

In  remodeling  the  Niagara  plant  Westinghouse  low-equivalent 
arresters  were  installed,  as  shown  in  Fig.  408.  These  protect  a 
22,000  volt  system.  Each  phase  of  each  circuit  has  an  arrester. 
They  are  mounted  on  marble  boards  and  each  board  is  mounted 
on  castors,  so  that  if  damaged  it  may  be  wheeled  out  and  replaced 
by  a  spare.  The  arresters  are  connected  to  the  feeder  line 
through  fuses. 


KAAAAAAAAAAAA 


FIG.  408. 

TRANSFORMERS. 

The  office  of  the  transformer  is  to  change  the  voltage  of  an 
alternating  current  circuit  from  one  value  to  another,  or  to 
change  the  system  from  one  phase  to  another.  They  come  in  all 
sizes,  from  the  potential  transformer  used  on  switch  boards  for 
voltmeters  to  those  of  thousands  of  watts  capacity. 

In  the  large  transformers  above  25  kw.  and  below  75  kw.  the 
case  is  usually  filled  with  oil,  which  serves  as  an  insulator.  In 
some  this  oil  is  pumped  in  and  out  and  cooled,  while  in  others 
the  case  is  given  a  large  area  to  dissipate  the  heat  by  radiation. 
Still  others  are  air  cooled,  a  blower  being  constantly  at  work 
forcing  air  through  the  transformer. 

In  the  power  house  we  have  to  deal  with  the  small  transformers 


416 


HYDROELECTRIC  PLANTS, 


used  in  connection  with  the  switchboard  instruments  and  the 
large  step  up  transformers  connected  to  the  main  lines. 

The  switch  board  potential  transformers, etc.,  are  only  large 
enough  to  serve  the  instruments  and  are  not  intended  to  carry 
a  load.  They  come  all  ready  to  place  on  the  switch  board  and 
need  no  description. 

The  same  type  of  transformer  is  used  for  any  number  of 
phases,  a  separate  transformer  being  placed  in  each  phase. 

The  following  are  the  methods  of  cooling: 

(1)  Self-cooling  dry  transformer,  made  for  voltages  up  to  15,000 

(2)  Self-cooling  oil-filled     "  "  "      80,000 

(3)  Cooled  by  forced  air  curents      "      " 
4)        "         "     "     water      "  "      " 
(5)  Cooled  by  both  oil  and  water     "      " 

The  over-heating  of  the  transformer  must  be  carefully  guarded 
against  and  should  never  run  above  80°  degrees  Centigrade. 
Thus,  if  the  temperature  of  the  room  is  40  degrees  Centigrade 
the  interior  of  the  transformer  must  not  exceed  it  by  more  than 
40  degrees  Centigrade. 

Types  (1)  and  (2)  are  more  expensive  to  build  than  the  other 
types,  as  more  iron  has  to  be  used,  but  are  the  best,  all  things 
considered. 

The  air  cooled  transformers  are  provided  with  air  pipes  con- 
necting with  a  blower.  In  large  plants  they  are  set  over  air- 
tight rooms  or  pipes  having  openings  in  the  ceiling  through 
which  the  air  passes  to  the  transformers  setting  over  the  holes. 
The  air  pressure,  amount  of  air,  etc.,  is  given  in  Table  L. 

TABLE  L 
DATA  ON  THE  COOLING  OF  AIR-BLAST  TRANSFORMERS. 


Totai 
capacity 
of  trans- 
formers, 
kw. 

Capacity 
of  trans- 
formers, 
kw. 

Ounce 
pressure 
per 
cu.  in. 

Cu.  ft.  air 
required 
per  min. 
per 
transformer 

Size  of 
blower, 
inches  . 

Speed  of 
blower, 
r.p.m. 

Output  of 
blower 
cu.  ft. 
per  min. 

Power  to 
drive 
blower, 
h.p. 

300 

50 

.30 

250 

40 

375 

1,800 

.25 

900 

100 

.40 

350 

50 

350 

3,200 

.60 

1800 

200 

.50 

600 

CO 

325 

5,900 

1.10 

2700 

300 

.GO 

850 

70 

310 

8,300 

2.25 

4500 

500 

.80 

1.300 

80 

310 

13,000 

4.25 

6700 

750 

.90 

1,800 

90 

295 

17,600 

6.75 

7500 

1  ,250 

1.00 

3.000 

100 

280 

23,600 

12.00 

POWER  HOUSE  EQUIPMENT. 


417 


The  power  consumed  in  cooling  an  air  cooled  transformer  is 
about  0.3  per  cent.,  or  less,  of  the  power  delivered. 

The  approximate  cost  of  transformers  is  from  $4  to  $7  per  kw. 

An  oil  cooled  transformer  may  simply  have  its  case  filled 
with  oil,  or  the  oil  may  be  circulated  by  means  of  a  pump.  The 
case  is-  sometimes  rilled  with  oil  and  water  caused  to  circulate 
around  and  through  the  case  to  cool  the  oil.  About  one  gallon 
of  water  per  minute  per  300  kw.  is  necessary  in  this  case.  These 
artificially  cooled  transformers  are  smaller  in  size  than  those 
depending  alone  on  the  radiation  of  the  cases,  but  have  the  dis- 
advantage that  should  the  pumps  or  blowers  fail  to  act  the  tem- 
perature will  run  up.  However,  such  transformers  will  stand 
such  usage  for  an  hour,  and  most  faults  can  be  remedied  in  that 
time.  The  pumping  outfit  should  in  all  cases  consist  of  two 
separate  pumps. 

Thin  transformer  cases  should  be  avoided,  as  in  case  of  fire 
they  become  punctured  and  the  oil  escapes.  The  casing  should 
be  at  least  £-inch  thick. 

TABLE  LI. 


Watts 
capacity. 

Core 

loss 
watts. 

Full  load 
copper 
loss    in 
watts. 

Regula- 
tion 
per  cent  . 

Efficiency. 

Weight 
in  Ibs. 

Approx. 
cost. 

Full 
load. 

1  load. 

i  load. 

i  load. 

600 

25 

16.7 

2.93 

93.5 

92.9 

91.1 

85.2 

70 

1,000 

32 

27.4 

2.80 

94.4 

94.0 

92.8 

88.1 

95 

1,500 

38 

37.5 

2.63 

95.2 

95.0 

94.0 

90.3 

125 

2,000 

45 

50.0 

2.58 

95.5 

95.4 

94.5 

91.2 

155 

2,500 

50 

54.0 

2.23 

96.0 

95.9 

95.1 

92.1 

195 

3,000 

55 

62.0 

2.13 

96.2 

96.1 

95.5 

92.7 

220 

4,000 

63 

85.0 

2.19 

96.4 

96.4 

95.9 

93.6 

270 

5,000 

70 

105.0 

2.17 

96.6 

96.6 

96.2 

94.2 

350 

7,500 

110 

147.0 

2.50 

96.7 

96.6 

96.2 

94.6 

470 

10.000 

140 

177.0 

1.90 

96.9 

96.9 

96.4 

94.3 

535 

15,000 

175 

272.6 

1.90 

97.2 

97.1 

96.8 

95.1 

850 

20,000 

190 

356.0 

.94 

97.3 

97.4 

97.2 

95.9 

995 

25,000 

220 

460.0 

.98 

97.3 

97.5 

97.3 

96.1 

1210 

30.000 

250 

495.0 

.81 

97.5 

97.7 

97.5 

96.3 

1500 

40,000 

390 

590.0 

.65 

97.6 

97.6 

97.4 

95.8 

1780 

50,000 

460 

690.0 

.48 

97.7 

97.7 

97.5 

96.1 

1900 

The  transformer  is  the  weak  link,  and  every  precaution  must 
be  taken  for  its  protection.  If  there  is  a  break-down  on  the 
system  the  chances  are  three  to  one  that  the  fault  is  with  the 


418 


HYDROELECTRIC  PLANTS. 


transformers.  Lightning  is  the  most  dangerous  foe  and  hence 
the  latest  and  best  arresters  are  none  too  good.  A  good  plan, 
suggested  by  Professor  Thomson,  is  that  of  interposing  a  metallic 
shield,  connected  to  earth,  between  the  primary  and  secondary 
windings. 

Another  safety  device  invented  by  Professor  Thomson  con- 
sists of  a  thin  paper  film  between  two  metallic  points,  one  of 
which  is  connected  to  the  line  and  the  other  to  the  ground.  This 
automatically  grounds  the  line,  though  it  is  not  at  all  certain  to 
act. 

One  of  the  heroic  measures  for  protection  is  to  ground  the 
secondary  circuit.  This  is  now  permitted  by  the  underwriters. 
All  secondary  circuits  should  be  frequently  tested  for  shorts. 
This  is  done  by  running  test  wires  to  the  transformers  and  test- 


u 


u 

4$$ 


•n 


iS-S-3- 


LIH2I 

a    cb 


FIGS.  409-412. 

ing  with  a  ground  detector  on  the  board.  Each  year  a  complete 
insulation  test  should  be  made  of  every  transformer.  Trans- 
formers are  also  inserted  in  the  primary  to  add  to  the  protection 
given  by  the  arresters.  The  cases  of  all  large  station  trans- 
formers should  be  thoroughly  grounded  to  protect  the  workmen. 

Figs.  409-412  show  the  most  common  methods  of  connecting 
the  ordinary  protective  devices. 

Transformers  being  almost  invariably  used  for  constant  poten- 
tial circuits  they  must  be  protected  against  heavy  surges  of 
current  due  to  shorts  on  the  line.  The  fuse,  therefore,  becomes 
a  very  important  part  of  the  transformer. 

The  Stanley  Company,  the  General  Electric  Company,  West- 
inghouse  and  many  others  make  fuses  especially  for  transformers. 
They  have  removable  blocks,  so  that  the  fuses  may  safely  be 
replaced.  Transformers  may  be  wound  tor  polyphase,  but  the 


POWER  HOUSE  EQUIPMENT.  419 

best  practice  is  to  use  the  single  phase.  Though  requiring  more 
iron  the  single  phase  arrangement  permits  the  banking  of  the 
transformer,  so  that  the  disabling  of  one  does  not  completely 
cripple  the  system. 

In  selecting  the  size  and  efficiency  of  transformers  it  must 
be  borne  in  mind  that  it  is  not  always  best  practice  to  install 
transformers  of  the  highest  efficiency.  The  more  efficient 
transformers  are  higher  priced,  and  when  the  difference  between 
the  costs  of  two  transformers  becomes  greater  than  the  power 
saved  by  the  more  efficient  transformer  could  be  sold  for,  the 
cheaper  transformer  would  be  the  proper  one  to  adopt. 

The  best  power  house  practice  is  to  use  four,  six,  ten  or  more 
transformers  banked  together  and  having  one  transformer  in 
reserve  ready  to  be  rolled  into  place.  There  is  always  danger  of 
a  transformer,  especially  the  oil  cooled  type,  catching  fire,  and 
it  is  quite  important  to  provide  for  such  contingencies.  They 
should  be  in  a  separate  room  arid  have  switches  arranged  on  their 
cases  so  that  by  merely  opening  the  switch  the  transformer  is 
disconnected  from  the  line  and  ground.  It  is  a  good  plan  to 
have  each  transformer  mounted  on  a  truck  to  facilitate  quick 
movement. 

Never,  under  any  circumstances,  install  a  cheap  transformer. 
The  standard  transformers  are  quite  reliable,  but  those  which 
are  not  well  known  should  be  avoided.  Table  LII  gives  the 
proper  sizes  for  transformers  on  three-phase  motor  circuits. 

Transformers  will  carry  as  great  an  overload  as  the  generators, 
so  their  normal  rating  should  be  the  same  as  that  of  the  gen- 
erators. 

Small  transformers,  below  25  kw.,  may  be  placed  on  poles. 
The  common  practice  nowadays,  however,  is  to  use  a  few  large 
transformers  at  sub-stations  rather  than  numerous  small  ones 
mounted  on  poles  at  the  houses.  It  is  not  good  practice  to 
mount  transformers  on  the  walls  of  houses,  though  at  times  this 
has  to  be  done,  in  which  case  precautions  must  be  taken  to  insu- 
late them  from  the  brick  or  woodwork. 

Parallel  connection  is  not  advisable  for  small  transformers 
where  it  can  be  avoided. 

Transformers  are  often  wound  in  sections,  so  that  for  high  vol- 
tage they  may  be  connected  in  series. 

Where  it  is  wished  to  increase  the  primary  voltage  on  an  old 


420 


HYDROELECTRIC  PLANTS. 


TABLE  LII. 
PROPER  CAPACITY  OF  TRANSFORMERS  FOR  S-PHASE   MOTORS. 


Capacity  of 
\Iotor  in  h.p. 

Capacity  of 
transformers  in  kw. 

Two 

transformers. 

Three 
transformers. 

1 

O.G 

0.0 

2 

1.5 

1  .0 

3 

2.0 

1.5 

5 

3.0 

2.0 

7* 

4.0 

3.0 

10 

5.0 

4.0 

15 

7.5 

5.0 

20 

10.0 

7.5 

30 

15.0 

10.0 

50 

25.0 

15.0 

75 

25.0 

system,  the  primary  windings  of  the  old  transformers  may  be 
connected  in  series. 

In  four- wire,  two-phase  systems,  unless  motors  are  to  be 
operated,  the  transformers  are  connected  to  each  phase  in  the 
same  manner  as  for  a  single  phase,  but  where  motors  are  run  there 


E 
V3 


FIG.  413. 


FIG.  414. 


must  be  one  transformer  for  each  phase,  each  having  a  capacity 
of  one-half  that  of  the  motor  or  its  rated  overload. 

In  three-phase  work  two  types  of  connections  are  used, 
namely,  the  delta,  J,  and  the  star,  Y,  connections.  The  relative 
voltages  and  currents  for  1:1  ratio  are  given  in  Figs.  413  and 
414. 


POWER  HOUSE  EQUIPMENT.  421 

Transformers  may  be  used  as  phase  changers  (see  Fig.  415). 
That  is,  a  two-phase  generator  may  be  installed  in  the  power 
house  and  the  current  changed  to  three-phase  for  transmission. 
This  might  be  advisable  where  a  part  of  the  load  is  near  by. 
This  is  the  system  at  Niagara  and  in  Fig.  415  are  shown  the 
connections  for  changing  from  two-phase  to  three-phase  and 
then  from  three-phase  back  to  two-phase. 

One  transformer  should  have  a  transformation  ratio  of  100:10 
and  the  other  100:8.67.  This  latter  ratio  for  small  transforma- 
tion is,  in  practice,  made  at  100:9.  If  the  two  transformers  are 
wound  the  same  or  are  interchangeable  they  must  have  a  com- 
bined capacity  of  12  per  cent,  more  than  the  load.  The  100:9 
transformer  is  called  a  teaser  and  need  be  but  4  per  cent,  larger 
than  would  be  normally  required.  For  transforming  the  phases 
two  transformers  are  usually  used,  which  are  made  especially 


FIG.  415. 

for  the  work,  having  two  connections,  one  giving  50  per  cent, 
and  the  other  86. 7  per  cent,  the  full  voltage.  In  this  case  either 
transformer  may  serve  as  the  teaser. 

STORAGE  BATTERY. 

The  storage  battery  is  seldom  used  essentially  in  its  storage 
sense,  its  cost  prohibiting  this,  but  invariably  in  the  capacity  of 
a  regulator.  Its  importance  is  in  almost  direct  proportion  to 
the  rapidity  and  magnitude  of  the  fluctuations.  The  cost  of  a 
storage  battery  plant  is  high,  but  in  all  cases  of  engineering  the 
only  disideratum  should  be  the  relation  between  the  total  first 
cost  and  the  future  dividends,  and  when  so  considered  the  use 
of  a  battery  plant  will  usually  become  a  necessity  for  the  follow- 
ing reasons: 

(1)  The  capacity  of  the  generating  units  required  to  carry 
the  abnormal  peak  loads  is  decreased,  thus  minimizing  the  first 
cost  of  the  plant. 


422  HYDROELECTRIC  PLANTS. 

(2)  The  maintenance  of  better  voltage  regulation  on  the  whole 
system. 

(3)  The  creation  of  a  reserve  force  which  may  be  utilized  to 
carry  a  minimum  load  for  a  short  time  to  permit  of  repairs,  etc. 

(4)  A  reduction  in  the  annual  cost  of  producing  a  unit  of 
energy.     A  generating  unit,  when  run  at  full  load,  is  from  10  to 
30  per  cent,  more  efficient  than  when  running  on  such  loads  as 
are  common  to  all  power  plants  not  equipped  with  batteries. 
The  wear  and  tear  on  a  plant  carrying  a  fluctuating  load  is  quite 
severe,  and  plays  an  important  part  in  the  depreciation  item. 
Especially  is  this  true  of  a  turbine  plant  where  the  action  of  a 
powerful  governor  on  the  gates  causes  great  wear  and  vibrations. 

(5)  Increase  of  the  capacity  of  transmission  lines  by  carrying 
the  peak  loads  at  the  point  of  use,  thus  making  the  line  only 
carry  the  normal  load. 


FIG.  416.  FIG.  417. 

The  most  prominent  makers  of  batteries  are  the  Electric 
Storage  Battery  Company  of  Philadelphia  and  the  Gould  Stor- 
age Battery  Company  of  New  York.  The  Electric  Storage 
Battery  Company  build  the  chloride  battery  and  the  Gould 
Company  the  Gould  battery. 

For  central  station  use,  the  cells  are  best  made  in  the  form  of 
lead  lined  wooden  tanks,  eac.h  cell  or  tank  lining  made  somewhat 
longer  than  necessary  to  hold  the  plates  first  installed,  so  as  to 
allow  more  plates  to  be  added  later  on  if  found  advisable.  Being 
receptacles  for  the  storage  of  energy  under  electrical  pressure 
the  cells  themselves  must  be  thoroughly  insulated  from  the  earth. 
This  may  be  accomplished  by  placing  each  cell  in  a  box  of 
sand  as  in  Fig.  416,  and  setting  the  box  on  four  oil  insulators, 
shown  in  Fig.  417,  or,  as  is  most  frequently  done,  on  porcelain 
insulators. 

The  room  must  be  provided  with  special  ventilation  to  carry 
off  the  acid  fumes.  The  frame  work  supporting  the  cells  must 


POWER  HOUSE  EQUIPMENT.  423 

be  very  strong,  of  wood  and  painted  with  an  acid-proof  paint. 
The  plates  contained  in  the  cell  constitute  the  element.  The 
connections  are  all  made  by  burning  the  terminals  together. 

Great  care  must  be  taken  to  get  pure  acid  and  distilled  water. 
The  capacity  of  storage  batteries  is  given  in  ampere-hours  or 
watt-hours  under  a  certain  rate  of  discharge.  Every  battery 
has  Its  most  efficient  rate  and  if  this  is  exceeded  the  capacity  is 
lessened.  If  a  cell  can  deliver  100  amperes  for  10  hours  on 
normal  discharge  its  capacity  will  be  1000  ampere-hours,  but 
If  discharged  in  five  hours  its  capacity  may  only  be  800  ampere- 
hours.  For  this  reason  a  sufficient  number  of  batteries  should  be 
installed  to  carry  at  least  75  per  cent,  of  the  peak  on  a  normal 
discharge. 

The  watt-hour  capacity  is  more  trustworthy  than  the  ampere- 
hour,  for  while  the  latter  efficiency  may  be  as  high  as  95  per  cent, 
the  former  is  seldom  above  70  per  cent,  to  80  per  cent. 

The  new  Edison  battery  weighs  57  pounds  per  kw.-hour 
capacity,  and  has  a  voltage  per  cell  of  from  1.1  to  1.5  volts. 
A  battery  having  a  capacity  of  1000  kw.-hour  capacity  will,  if  all 
cells  are  on  the  same  floor,  take  up  about  100  square  yards. 

The  largest  cells  may  consist  of  from  80  to  100  plates.  A 
single  cell,  such  as  used  in  the  power  house,  gives  from  6  to  7 
ampere-hours. 

Storage  batteries  must  be  charged  at  a  slightly  higher  voltage 
than  they  are  discharged  at.  This  charging  voltage  averages 
from  2  to  2.5  volts  per  cell,  and  the  discharging  voltage  will 
average  from  2.5  to  1.8. 

While  charging,  the  voltage  is  gradually  increased  so  that 
two  cells  may  require  40  volts  at  the  start  and  50  at  the  finish. 
This  is  usually  done  by  means  of  the  booster  or  cutting-out 
resistance  from  the  generator  field.  Without  some  regulating 
device  the  voltage  delivered  to  the  line  would  drop  off  from 
20x2.5  =  44  volts  to  1.8x20  =  36.0  volts. 

To  counteract  this  drop  cells  are  added  so  that  they  may  be 
thrown  in  one  after  another  to  keep  up  the  pressure.  These  are 
called  end  cells. 

Cells  should  never  be  completely  discharged,  1.8  volts  being 
the  minimum  voltage  of  the  discharge. 

To  get  the  desired  voltage  for  any  system  enough  batteries 
are  placed  in  series  to  give  it:  thus: 


424 


HYDROELECTRIC  PLANTS. 


Desired  Battery  Voltage  . 

T-TT—  :  -  r—  -  -  7  —  ^h  —  =  number  of  cells. 
Minimum  voltage  of  cell. 

Then  to  get  the  desired  current  groups  of  the  cells  in  series  as 
given  by  the  above  formula  are  connected  in  parallel,  as  in  Fig. 
418,  where  each  cell  has  a  capacity  of  10  amperes. 

Sometimes  there  are  not  enough  cells  to  take  up  the  voltage 
of  the  machine  ,  in  which  case  a  resistance  is  placed  in  series  with 
the  cells.  The  amount  of  this  resistance  is  found  by  dividing 
the  difference  between  the  voltage  of  the  batteries  and  the  gen- 
erators, by  the  amperage  of  the  battery. 

The  usual  office  of  a  storage  battery  makes  it  necessary  to 
automatically  cause  the  cells  to  be  charged  during  hours  of  light 
load  and  discharged  during  peak  loads. 

In  large  plants,  such  as  we  are  more  especially  treating,  the 
regulation  of  the  battery  must  be  more  rapid  than  hand  regula- 
tion, and  therefore  a  booster  is  used.  This  booster  is  a  small 


FIG.  418. 

generator  usually  driven  by  a  motor,  and  its  action  is  as  follows: 
The  battery  and  the  armature  of  the  booster  are  in  series. 
The  booster  field  has  two  windings,  one  is  a  fine  wire  shunt,  and 
the  other  a  few  turns  of  heavy  wire  in  series  with  the  main  line. 
The  field  current  may  be  adjusted  by  means  of  a  shunt  rheostat. 
The  effect  of  the  booster  is  that  of  a  number  of  cells  added  in 
series  with  the  battery. 

The  shunt  and  field  coils  of  the  booster  oppose  each  other  in 
such  a  way  that  on  normal  discharge  there  is  no  e.m.f.  generated. 
But  when  the  line  current  falls  below  normal,  the  shunt  coil, 
excited  by  the  battery,  takes  effect  and  the  booster  delivers  an 
e.m.f.  which  aids  the  generator  in  charging  the  batteries.  When 
the  line  current  is  above  normal  due  to  a  heavy  load  on  the  line, 
the  series  coil  takes  effect  and  forces  the  battery  into  helping 
carry  part  of  the  load. 


POWER  HOUSE  EQUIPMENT.  425 

The  electrolyte,  consisting  of  sulphuric  acid  and  water,  must 
be  of  the  purest  ingredients.  The  water  is  placed  in  the  cell 
first  and  the  acid  poured  slowly  into  the  water.  After  the 
mixture  has  cooled  and  within  two  hours,  the  plates  are  placed 
in  position,  connected,  and  the  batteries  slowly  charged.  It  is 
advocated  by  some  makers  to  charge  the  batteries  for  the  first 
time  at  about  one-third  the  normal  rate.  Charging  at  a  higher 
rate  than  recommended  by  the  makers  should  never  be  attempted 
A  little  overcharging  does  no  harm,  but  results  in  a  waste  of 
current. 

When  the  cells  are  fully  charged  the  following  facts  are  ap- 
parent: Number  of  ampere-hours,  i.e.,  the  product  of  the  reading 
of  the  ammeter  and  the  time  comes  to  the  desired  amount;  the 
voltage  reaches  the  maximum;  the  positive  plate  becomes  very 
dark;  gasing  takes  place,  that  is,  gas  is  given  off,  making  the 
electrolyte  boil.  When  this  last  phenomenon  has  gone  on  10 
or  15  minutes  the  battery  is  charged. 

To  prevent  the  escape  of  the  gas  the  electrolyte  is  often 
covered  an  inch  deep  with  paraffine  and  an  inch-hole  bored 
through  to  prevent  the  accumulation  of  pressure.  Every  cell 
must  be  easily  accessible  for  examination  and  the  plates  and 
electrolyte  frequently  inspected.  The  plates  become  buckled  in 
time  and  particles  of  the  paste  fall  out  and  lodge  between  them. 
For  this  reason,  frequent  inspection  is  necessary  to  prevent  short 
circuiting  of  the  plates.  Each  cell  must  be  thoroughly  insulated 
from  the  earth.  Cells  should  not  be  left  standing  for  any  great 
length  of  time  without  being  charged,  else  sulphating  will  take 
place.  Sulphating  causes  a  scale  to  form  over  the  plates,  espe- 
cially on  the  positive  plates,  reducing  the  capacity  of  the  cell  and 
causing  a  buckling  of  the  plates.  Sulphating  is  removed  by 
carefully  scraping  the  plates,  after  which  they  are  charged  at  a 
slow  rate  for  some  time.  If  a  storage  battery  is  to  be  put  out  of 
use  for  any  great  length  of  time,  they  should  be  fully  charged, 
the  electrolyte  drawn  off  and  the  cells  then  filled  with  pure  water. 
They  should  then  be  discharged  at  their  normal  rate.  After  the 
water  has  stood  in  the  cells  for  some  48  hours  it  is  then  drawn  off 
and  the  battery  will  remain  in  good  condition.  If  the  plates 
become  slightly  buckled  they  may  be  straightened  by  pressing, 
not  pounding,  between  two  boards. 

In  Fig.  419  and  420  are  given  two  load  curves  which  were 


426 


HYDROELECTRIC  PLANTS. 


taken  at  a  large  lighting  and  power  station.  The  curve  in  Fig. 
419  is  a  representative  winter  curve,  and  that  shown  in  Fig.  420 
was  taken  in  the  spring.  The  double  hatched  portion  shows 


1    i'  |  I    1*1    i*  I    I    1*1   l'  I   I    I   I   I    I  I 


FIG.  419. 

the  load  carried  by  the  battery,  and  the  single  hatched  shows 
the  charging  load  of  the  power  plant.  The  battery  was  of  the 
chloride  type,  having  a  10,000  kw.-hr.  capacity. 


Vtof. 


FIG.  420. 

It  will  be  seen  that  the  maximum  peak  load  amounts  to  1600 
kw.  above  the  average.  That  is,  had  there  been  no  battery  used, 
1600  kw.  more  power  would  necessarily  have  been  generated  by 


POWER  HOUSE  EQUIPMENT.  427 

machinery.  Aside  from  the  first  cost,  interest  and  depreciation 
of  all  this  added  machinery,  it  would  have  worked  at  full  load 
only  a  small  part  of  the  day,  so  that  its  efficiency  would  have 
been  very  low.  If  the  power  had  been  generated  by  steam  the 
boilers  necessary  for  the  peak  loads  would  all  have  to  be  heated 
up  and  then  allowed  to  cool  down — a  very  costly  and  injurious 
thing  to  do.  The  use  of  the  storage  battery,  therefore,  equalizes 
the  load  and  permits  a  lesser  number  of  generating  units  to  work 
at  their  most  efficient  output. 

In  Fig.  419  it  will  be  seen  that  the  batteries  could  have  easily 
carried  all  the  load  there  was  between  1  and  5  a^m.,  if  it  had 
been  necessary  for  a  short  time.  However,  if  the  battery  had 
been  installed  with  this  point  in  view  more  battery  power  would 
have  been  required,  as  it  is  during  those  hours  that  the  batteries 
must  be  charged. 

The  efficiency  of  a  storage  battery  being  about  70  per  cent, 
the  power  of  the  machinery  must  be  so  proportioned  that  the 
double  shaded  portion  of  the  power  curves  is  70  per  cent,  of  the 
single  shaded  portion,  i.e.,  the  battery  should  have  a  capacity 
30  per  cent,  larger  than  the  double  shaded  portion. 

In  designing  a  plant,  curves  should  be  drawn  approximating 
as  nearly  as  possible  what  the  actual  practice  will  be,  and  the 
battery  and  machine  capacity  worked  out  from  them ;  then  after 
the  plant  is  in  operation  the  curves  may  be  brought  to  the  desired 
form  by  regulating  the  charges  for  current. 

To  generate  the  1600  kw.  by  steam  would  cost,  for  machinery, 
about  $130,000,  and  the  added  yearly  maintenance  cost  of  the 
machinery  would  be  about  as  follows: 

Depreciation   at  8  per  cent,   on   $130,000   worth   of 

machinery $10,400 

Interest  and  insurance  on  $130,000  worth  of  machinery     8,000 
Added  cost  of  operating  $130,000  worth  of  machinery . .     4,000 
2  per  cent,  added  depreciation  due  to  operating  4860 
kw.,  or  $390,000  worth  of  machinery  on  uneven  loads  7,800 


$30,200 

To  get  the  watt-hour  capacity  of  the  battery  multiply  the 
hours  the  load  is  on  by  the  average  watts:  thus  take  the  case  of 
the  first  peak  in  curve,  Fig.  419;  the  average  time  is  4J  hours 


428 


HYDROELECTRIC  PLANTS. 


and  the  average  load  is  about  1000  kw.,  which  makes  4250  kw.- 
hrs.,  as  the  capacity  required  for  that  part  of  the  load.  Each 
peak  is  figured  in  the  same  way  and  the  sum  multiplied  by  1 . 3 
gives  the  necessary  capacity  of  the  battery. 

In  the  above  case  the  required  10,000  kw.-hr.  battery  would 
cost  $40,000  and  the  yearly  cost  of  operation,  depreciation, 
interest,  etc.,  would  be  about  $4000.  Several  companies  guar- 
antee the  maintenance  to  be  5  per  cent,  or  less. 

Fig.  421  shows  the  load  curves  on  a  large  central  station  plant 
for  a  week  day  and  for  Sunday.  Taking  the  week  day  card: 
The  station  was  provided  with  a  1000  kw.  unit  which  was  thrown 
on  to  the  load  at  12  a.m.  It  carried  the  load  with  good  efficiency 
until  about  7  o'clock,  when  another,  a  3500  kw.,  unit  was  thrown 


in.  At  this  time  the  ammeter  did  not  show  up  a  full  load  so  the 
storage  battery  was  connected  and  charging  commenced.  The 
ammeter  showed  the  load  was  increasing  on  the  line,  so  at  2.30 
a  1500  kw.  unit  was  put  into  service  and  the  battery  thrown 
out  until  3  p.m.,  when  the  battery  was  put  into  the  line.  The 
three  units  kept  up  their  load  until  midnight  by  feeding  the 
battery  as  shown.  In  this  case  the  battery  saved  4000  kw. 
capacity  in  machinery.  The  Sunday  card  shows  how  the  battery 
carried  the  entire  load  from  12  midnight  until  2  p.m. 

In  hydraulic  transmissions  the  battery  is  placed  at  the  far 
end  of  the  line  at  the  center  of  distribution.  For  alternating  cur- 
rents a  motor  generator  is  required  to  change  to  direct  current,  in 
which  case  an  attendant  is  required  constantly  at  the  sub-station. 
But  where  the  transmission  is  by  direct  current  only  an  occa- 


POWER  HOUSE  EQUIPMENT.  429 

sional  visit  to  inspect  the  battery  is  necessary,  the  booster  being 
located  at  the  power  house. 

The  location  of  the  battery  at  the  consumer's  end  of  the  line 
adds  another  valuable  feature  to  the  battery  installation.  It 
permits  the  use  of  a  smaller  feeder,  or  for  the  same  size  of  wire 
reduces  the  line  drop.  This  is  because  the  peak  current  is  never 
sent  over  the  line,  the  battery  supplying  all  excesses.  Old  plants 
find  this  method  a  good  one  for  increasing  their  capacity  without 
changing  the  size  of  feeders  or  installing  extra  machinery. 

On  lighting  loads  a  booster  is  used  only  to  add  a  few  volts  to 
the  generators,  but  on  railway  work  the  booster  is  so  made  that 
it  regulates  the  batteries,  causing  them  to  charge  and  discharge. 

An  end-cell  switch  is  used  in  connection  with  the  boosters. 
This  sometimes  consists  of  a  sliding  contact  caused  to  move 
along  the  threaded  shaft  by  means  of  a  small  motor  made  espe- 
cially for  the  purpose.  A  double  throw  single-pole  switch  is 
used  to  connect  the  battery  either  to  the  generator  through  the 
booster  or  directly  to  the  line. 

MOTOR  GENERATORS. 

Motor  generators  are  motor-driven  generators.  They  com- 
monly consist  of  a  synchronous  motor  driving  a  direct  current 
generator  on  either  end  of  its  shaft.  The  losses  are  those  due  to 
a  synchronous  motor  and  the  losses  of  the  two  direct  current 
generators. 

The  most  common  use  for  the  motor-generator  is  for  convert- 
ing alternating  current  into  continuous  current  for  electric  rail- 
ways, though  it  is  also  frequently  used  for  lighting  and  power. 
In  this  way  power  may  be  transmitted  by  three-phase  current 
to  great  distances  and  then  changed  to  direct  current  for  the  use 
of  the  consumer.  It  serves  the  same  purpose  as  the  synchronous 
converter,  but  differs  from  the  converter  in  that  it  operates 
perfectly  on  the  higher  frequencies. 

FREQUENCY  CHANGERS. 

The  frequency  may  be  changed  to  suit  the  requirements  by 
using  a  frequency  changer.  This  consists  of  a  synchronous  motor 
directly  connected  to  an  induction  motor.  The  current  to  be 
changed  is  led  into  the  stationary  field  winding  of  the  induction 
motor,  called  the  primary,  and  taken  from  the  rotor  called  the 


430 


HYDROELECTRIC  PLANTS. 


secondary.  The  frequency  and  voltage  of  the  out-put  will 
depend  on  the  speed  of  the  secondary.  If  the  frequency  is  to  be 
increased  the  induction  motor  must  be  driven  backwards,  and 
if  the  frequency  is  to  be  decreased  it  is  driven  forwards. 

To  change  a  frequency  of  40  cycles  to  60  cycles,  the  secondary 
would  be  run  backivards  at  half  speed,  and  to  obtain  25  cycles 
from  a  60  cycle  current,  the  secondary  would  run  forwards  at 
about  0.4  times  its  rated  speed.  The  capacity  of  the  primary 
will  have  the  same  proportion  to  the  out-put  that  the  initial 
frequency  has  to  the  final. 

In  table  LIII  data  for  a  frequency  changer  of  100  kw.  capa- 

TABLE  LIII. 
INDUCTION  MOTOR  AS  FREQUENCY  CHANGER. 


Initial 
fre- 
quency. 

Final 
fre- 
quency. 

Primary 
capacity 
of  ind. 
motor 
in  kw. 

Secondary 
capacity 
of  syn. 
motor 
in  kw. 

Capacity 
of  fre- 
quency 
changer 
in  kw. 

Speed 
of  ind. 
motor 
r.p.m. 

Speed 
of  syn. 
motor 
r.p.m. 

Direction  and 
speed  of 
running. 

40 

60 

33 

66 

100 

400 

800 

Half  speed  back. 

30 

60 

50 

50 

100 

400 

800 

Full  speed  back. 

25 

60 

58 

42 

100 

400 

800 

336  forward. 

60 

25 

42 

58 

100 

400 

800 

1920  r.p.m.back. 

60 

30 

50 

50 

100 

400 

800 

Half-speed  ahead. 

60 

40 

66 

33 

100 

400 

800 

Half-speed  ahead. 

city  are  given.  The  proportions  would  remain  the  same  for 
other  sizes. 

The  efficiency  would  not,  of  course,  be  100  per  cent.,  as  has 
been  assumed,  but  would  depend  on  the  efficiency  of  the  two 
motors  used.  In  each  there  would  be  a  loss  of  from  4  to  10  per 
cent.,  depending  on  the  size  and  running  conditions. 

When  driven  backwards  all  mechanical  losses  are  supplied 
by  the  driving  motor,  but  when  driven  forwards  the  frequency 
converter  may  supply  a  part  or  all  of  the  mechanical  losses  in 
the  set. 

The  object  of  a  frequency  changer  is  to  permit  the  use  of 
synchronous  converters  on  a  system  where  a  high  frequency 
is  demanded  and  to  reduce  line  drop.  A  synchronous  converter 
will  not  operate  satisfactorily  on  the  higher  frequencies,  about 


POWER  HOUSE  EQUIPMENT.  431 

25  being  the  best.  Lighting  service  demands  60  cycles  or  more, 
and  for  long  transmissions  25  cycles  gives  the  smallest  voltage 
drop.  Therefore,  to  reconcile  these  oppositions  recourse  is  had 
to  the  frequency  changer. 

ALIGNMENT  OF  MACHINERY. 

One  of  the  most  necessary  instruments  for  this  work  is  the 
architect's  level.  Such  an  instrument  costs  about  $60.  It 
should  be  a  14-inch  level  with  a  vernier  for  getting  angles. 

Reliable  straight  edges  are  indispensable.  These  should  be 
three  in  number  and  4,  6,  and  8  feet  long.  Fig.  422  shows  the 
best  form. 

Where  the  engineer  has  much  shaft  aligning  to  do  it  will  pay 
to  have  the  instrument  shown  in  Fig.  423.  The  blades  G  and 
frame  are  made  of  tool  steel.  By  turning  the  thumb  wheel  C 
the  screw  H  is  revolved  in  the  nut  at  F.  The  screw  turns  in  Z7, 
which  moves  up  and  down  with  it.  E  is  another  nut  in  which  the 


FIG.  422. 

left-handed  thread  on  the  screw  works.  In  operation  the  blades 
are  placed  astride  the  shaft  and  the  screw  run  down  till  it  just 
touches  the  top  of  the  shaft  to  be  aligned.  As  H  moves  down- 
ward the  nut  E  moves  upward.  In  this  way  the  pivot  of  the 
wings  B  always  remain  the  same  distance  from  the  center  line 
of  the  shaft.  This  makes  it  very  handy  where  the  line  shaft 
consists  of  several  different  sizes.  In  leveling  the  point  A  is 
brought  into  line  with  the  tight  wire.  To  get  the  shaft  level 
in  the  horizontal  plane  the  architects'  level  is  set  up  and  the 
pivot  B  is  leveled  at  different  points  along  the  shaft. 

Plumb  lines  should  be  very  fine  silk  lines  or  steel  wire. 
Plumb  bobs  should  be  heavy.  Those  filled  with  quick  silver 
and  weighing  several  pounds  are  the  best. 

After  the  shafting  is  all  in  place  it  should  be  given  a  very 
careful  aligning.  The  loss  of  power  in  shafting  is  mostly  due  to 
poor  alignment. 

Where  the  bearings  of  a  line  shaft  pass  over  masonry  walls 


432 


HYDROELECTRIC  PLANTS. 


the  bearings  are  anchored  to  the  wall,  as  in  Fig.  424.  The  taper- 
ing boxes  A  should  be  well  made,  planed  perfectly  smooth  on 
the  outside  and  where  placed  in  concrete  well  soaped  or  oiled. 
After  the  base  of  the  bearing  is  placed  and  aligned  the  holes  left 
by  the  removal  of  the  boxes  are  filled  with  1  to  1  cement-sand. 
At  least  i  inch  is  left  between  the  bottom  of  the  bearing  base  and 


FIG.  423. 

the  top  of  the  masonry.  This  is  to  allow  for  any  small  error  in 
the  first  alignment  and  to  permit  pouring  underneath  the  iron, 
and  also  into  the  bolt  holes,  a  strong  mixture  of  cement. 

The  tapering  holes  left  by  the  boxes  allow  of  shifting  the  bolt 
heads  two  inches  or  more  each  way  before  pouring  the  mixture. 
Fig.  424  shows  one  taper  box  removed,  and  the  bearing  in 
place  ready  to  pour.  The  foundation  bolts  for  engines  and  gen- 
erators are  made  in  the  same  way. 


POWER  HOUSE  EQUIPMENT. 


433 


To  avoid  making  a  mistake  in  the  spacing  of  the  bolts  a  tem- 
plate should  always  be  made,  having  the  holes  bored  to  exactly 
fit  those  in  the  base  of  the  bearing  or  bed-plate.  On  this  tem- 
plate the  center  lines  may  be  marked  to  aid  in  aligning. 

It  is  of  extreme  importance  on  extensive  work  to  make  accu- 
rate measurements.  Instrument  makers  now  make  steel  tapes 
which  at  a  certain  temperature  and  tension  are  exact.  Tension 
handles  are  made  by  Keuffel  &  Esser  Co.,  of  New  York,  so  that 
the  engineer  will  know  when  the  tension  is  exact.  A  scale  is 
also  made  giving  the  correction  for  different  temperatures. 
A  100-foot  tape  is  about  J  inch  longer  at  summer  heat  than  at 
the  standard  temperature  of  62  degrees  Fahrenheit.  The  en- 
gineer can  have  his  tape  certified  at  Washington  by  paying  a 
dollar  or  so  extra. 


Fie.  JIM. 


FIG.  425. 


When  working  around  power  houses,  the  great  foe  to  the  steel 
tape  is  rust.  The  tapes  may  be  nickel  plated  for  from  50 
cents  to  $2. 

The  common  way  to  get  a  line  at  right  angles  to  another  is  to 
measure  off  certain  distances  as  A  B  and  A  C  (Fig.  425),  and 
then  to  make  the  distance 


2  +  A  O- 
The  distances  usually  taken  are  6  and  8,  then 

V62+82  =  10 

Where  great  accuracy  is  required  greater  distances  may  be 
taken.  There  should  be  a  vernier  on  the  level,  in  which  case  it 
may  be  used  for  getting  right  angles. 


CHAPTER  VIII. 
POWER  TRANSMISSION 

There  are  in  general  four  ways  of  driving  machines  from  tur- 
bines, namely:  direct  connection;  gears  and  shafting;  belting; 
and  rope  drive. 

COUPLINGS. 

The  line  shaft  is  divided  up  so  that  there  are  as  many  lengths 
as  there  are  pinions.  Heavy  shafts  are  seldom  longer  than  20 
feet.  Couplings  are  used  to  connect  the  various  pieces.  These 
may  be  the  plain  disc  coupling,  the  plate  coupling  or  the  com- 
pression. 


The  proportions  of  a  disc  coupling  are  given  in  terms  of  the 
shaft's  diameter,  in  Fig.  426.  The  size  and  number  of  bolts 
used  to  hold  the  halves  together  may  be  found  from: 

horse  power  transmitted  x  33,000 
Velocity  of  one  bolt,  ft.  per  min.  XAfXGOOO  = 

N  =  number  of  bolts. ;  6000  =  safe  shearing  strength  per  square 
inch  of  bolt. 

Example:  There  is  500  h.p.  to  be  transmitted.  Shaft  speed 
225  r.p.m.  Diameter  of  circle  of  bolt  centers  16  inches.  N.  =  .6 

434 


POWER   TRANSMISSION.  43S 

bolts.     The  velocity  of  the  bolts  is  884  feet  per  minute,  therefore, 


500X33,000 

=   •  52 


884X6X6000 


mches. 


The  bolt  of  standard  size  nearest  to  this  area  is  J-inch. 

In  connecting  the  generators  a  coupling  is  often  used  which 
has  a  little  give-and-take  motion  called  a  wabbler,  so  that  if  the 
line  shaft  and  generator  are  not  quite  in  line  there  will  be  no 
binding.  (Fig.  427.) 


FIG.  427. 

A  jaw  clutch   coupling,   Fig.   428,  is  a  handy   arrangement 
where  it  is  necessary  to  uncouple  frequently  and  quickly. 


FIG.  428. 


FRICTION  CLUTCHES. 

The  friction  clutch  is  a  form  of  coupling  which  can  be  thrown 
in  while  one  shaft  is  at  full  speed.  They  are  made  in  all  sizes 
itp  to  several  thousand  horse  power. 

Clutches  should  be  used  only  where  absolutely  necessary,  as 
they  are  a  weak  link  in  the  chain  and  get  out  of  order  easily. 
The  bushings  should  be  of  bronze  and  self-oiling.  The  power 
transmitted  by  a  clutch  is  proportional  to  the  speed. 


436  HYDROELECTRIC  PLANTS. 

KEYS. 
Referring  to  Fig.  429,  all  dimensions  being  given  in  inches: 


for/»2,   /=        +  - 

Where  the  pinions  are  slid  on  the  shaft  there  should  be  two 
keys,  one  on  each  side  of  the  shaft.  They  should  fit  snugly,  but 
loose  enough  to  permit  the  gear  being  slid  back  by  hand.  Screws 
are  used  to  hold  the  key  and  gear  in  place. 


QUILL  SHAFTS. 

Fig.  430  shows  an  arrangement  by  means  of  which  a  gear  or 
machine  may  be  thrown  out  without  affecting  the  line  shaft. 
Thus  two  generators  may  be  placed  end  to  end  on  the  same  shaft, 
the  generator  next  to  the  turbines  being  attached  to  the  quill. 
Then  this  generator  may  be  thrown  out  without  stopping  No.  2. 
No.  2  may  be  uncoupled,  or  uii-clutched,  without  stopping  No.  1. 
While  certain  conditions  often  make  a  quill  advisable,  it  should 
be  avoided  where  possible,  as  it  introduces  complications. 

SHAFTING. 

In  the  every  day  transmission  of  power  by  shafting  a  large 
per  cent,  of  the  power  is  lost  due  to  poor  design.  If  the  shaft 
springs,  not  only  is  the  friction  of  the  bearings  increased,  but 
also  that  of  the  gearing.  Shafting  should  always  be  calculated 
for  bending  moments  and  torsional  moments. 

The  curves  in  Fig.  431  will  quickly  give  the  proper  size  of  shaft 
for  safe  tensile  strength  of  7500  and  shearing  of  6000  pounds 
per  square  inch.  Fig.  432  is  for  the  purpose  of  getting  the  size 
for  any  other  strength.  Thus,  if  we  find  by  Fig.  431  that  a 
6-inch  shaft  is  required  and  we  wish  to  know  the  proper  size  for 


POWER  TRANSMISSION. 


437 


a  safe  strength  of  20,000  pounds  per  square  inch ;  following  up  the 
vertical  ordinate  from  6,  Fig.  432,  it  strikes  the  20,000  pound 
curve  at  the  horizontal  line  which  indicates  a  4  J-inch  shaft. 


One  of  the  largest  of  manufacturing  plants  some  time  ago, 
while  building  their  plant,  guessed  at  the  size  of  some  shafts  on 
the  heavy  conveyors.  The  designer  had  figured  them  for  the 


FIG.  431. — Curves  giving  proper  size  of  shaft  for  given  twisting  and  bend- 
ing moments. 


FIG.  432. — Diagram  for  getting  new  diameters  when  shaft  has  been  figured 

from  Fig.  431 


POWER  TRANSMISSION. 


torsional  moments  alone.  When  the  plant  started  up  six  of  the 
24  shafts  broke,  and  the  author  learned  from  good  authority 
that  the  total  cost  caused  by  the  accident  amounted  to  over 
$20,000. 

Fig.  433  gives  the  proper  allowance  for  different  fits.  These 
curves  may  be  used  for  obtaining  the  size  of  bore  in  the  gears 
or  pulleys. 


FIG.  433. — Diameters  of  shafts  for  various  fits. 

The  following  formulas,  given  by  Thurston  and  modified  by 
Jones  &  Laughlins,  will  be  found  fairly  safe,  though  where  first 
class  work  is  desired  they  may  sometimes  give  a  shaft  too  small. 


For  head  shafts 
well  supported 
against   springing 


For  line  shafting 
hangers  8  feet 
apart 


For  transmission 
only,  no  pulleys; 

or 
short  counters 


H.P.  = 


H.P.  = 


H.P.  = 


H.P.  = 


<PR; 

125 


d3R 
90 


-;     d  = 


R 


for  iron. 

for    cold- 
rolled  iron. 

for  iron. 

for  cold- 
rolled  iron. 


50 

(PR 
30 


-    '/50HJP^fortumed 
\        R       iron. 


d  = 


3 / 30  H.P.   cold 


R 


iron. 


where  d  =  diameter  of  shaft  in  inches  and  R  =  r.p.m. 

*Is  proper    for    turbine   line   shafts   where  S  =    10,000    pounds    per 
Square  inch. 


440  HYDROELECTRIC  PLANTS. 

GEARS. 

The  most  common  method  of  driving,  aside  from  that  of  direct 
connection  is  by  means  of  gearing.  By  its  use  the  speed  of 
the  machine  may  be  made  higher  or  lower  than  that  of  the  tur- 
bine. Sometimes  the  ratio  is  as  high  as  4  to  1,  though  this  is 
uncommon.  The  limiting  factors  are  the  peripheral  speed  of  the 
cogs  and  the  number  of  teeth  on  the  pinion ;  the  former  must 
not  exceed  1800  feet  per  minute  for  iron  gears  and  2400  per 
minute  for  an  iron  gear  running  on  one  with  wooden  teeth .  These 
are  limiting  values  and  lower  speeds  should  be  used  where  possi- 
ble. 

The  makers  of  gear  wheels  publish  lists  of  their  patterns,  and 
in  selecting  the  gears  one  must  be  governed  by  these ;  taking  the 
nearest  patterns. 

There  are  three  types  of  gears  used  for  turbine  connections, 
namely,  mitre,  bevel  and  spur. 

Mitre  and  bevel  gears  are  the  same,  the  mitre  being  a  bevel 
gear  with  the  face  at  an  angle  of  45°  with  the  line  of  shaft.  That 
is,  both  gears  are  of  the  same  size. 

A  spur  wheel  is  one  having  the  face  of  the  teeth  parallel  with 
the  shaft.  One  of  a  pair  of  heavy  gears  should  always  be  a 
mortise  gear,  i.e.,  a  cast-iron  frame  with  wooden  teeth. 

There  are  two  kinds  of  teeth,  cyclodial  and  involute. 

The  former  type  is  most  common  for  ordinary  gear  wheels, 
while  the  latter  is  mostly  used  for  racks,  etc. 

The  circular  pitch  equals  the  length  of  the  arc  in  inches  be- 
tween the  centers  of  two  adjacent  teeth. 

The  diametral  pitch  is  given  by  the  number  of  teeth  per  inch 
of  the  diameter  of  the  pitch  circle. 

When  starting  the  design  of  a  gear  decide  on  the  pitch.  The 
number  of  teeth  in  the  wheel  should  not  be  divisable  by  the 
number  in  the  pinion. 

When  the  pinion  (smallest  gear)  is  driven  by  the  wheel  the 
number  of  teeth  in  pinion  should  not  be  less  than  eight.  When 
the  wheel  is  driven  by  pinion  the  number  of  teeth  in  the  pinion 
should  not  be  less  than  ten.  Having  selected  the  pitch  and 
knowing  the  revolutions  of  the  gear  and  velocity  along  the 
pitch  circle  which  is  considered  good  practice,  the  pitch  diameter 
is  found,  and  the  teeth  laid  out. 

Rule:     To  ascertain  the  revolutions  of  gearing  multiply  the 


POWER  TRANSMISSION.  441 

number  of  cogs  in  one  by  its  number  of  revolutions  and  divide 
the  product  by  the  number  of  cogs  in  the  other;  the  quotient 
will  be  the  number  of  revolutions  of  the  driven. 

Rule:  To  ascertain  the  number  of  cogs  in  one,  the  number 
of  its  revolutions  and  the  number  of  cogs  and  revolutions  of 
the  other  being  known,  multiply  the  number  of  cogs  in  the 
latter  by  the  number  of  its  revolutions,  and  divide  the  product 
by  the  number  of  revolutions  of  the  former;  the  quotient  will  be 
the  number  of  cogs  in  the  former. 

Rule:  Ascertain  the  pitch  diameter  of  cog  gearing,  multiply 
the  number  of  cogs  by  the  number  of  thirty-seconds  of  an  inch 
in  the  pitch  and  divide  by  n. 

Example  :     A  pitch  of  two  inches  has  sixty  -four  thirty-seconds 

120  +  64 

of  an  inch;  say  the   wheel  has  120  cogs;-^r  --  gives    76.39 


inches,  the  diameter  of  the  pitch  line. 

To  determine  the  horse  power  which  any  gear-wheel  will 
transmit,  four  facts  must  be  known,  namely: 

The  kind  of  wheel,  whether  spur,  bevel,  spur  mortise  or  bevel 
mortise  ;  the  pitch  ;  the  width  of  tooth  called  face  ;  the  velocity 
of  pitch  circle  in  feet  per  second. 

Generally  the  fourth  fact  is  not  known.  But  it  can  be  found 
if  the  pitch  diameter  of  the  wheel  (in  inches)  and  the  number 
of  revolutions  per  minute  are  given,  for  it  can  be  obtained  from 
them  by  the  following  rule: 

Rule  1.  Given  the  pitch  diameter  in  inches  and  the  number 
of  revolutions  per  minute;  to  find,  the  velocity  of  pitch  line  in 
feet  per  second. 

Multiply  the  pitch  diameter  (in  inches)  by  the  number  of  revo- 
lutions per  minute,  then  divide  the  product  thus  found  by  230; 
the  quotient  will  be  the  velocity  required. 

Example:  What  is  the  velocity  of  the  pitch  circle  of  a 
gear-wheel  in  feet  per  second,  the  pitch  diameter  =  43  inches, 
revolutions  per  minute  =  125. 

43  X  125  -f-  230  =  23.4  feet  per  second. 

For  heavy  gears  subject  to  constant  wear  the  pinion  should 
have  no  less  than  15  teeth.  0-ears  may  be  designed  having  a 
large  factor  of  safety  and  yet  work  at  a  pressure  which  will 
soon  wear  them  out.  In  one  of  the  most  noted  establishments 
in  the  United  States  the  practise  is  to  allow  very  low  pressures 


442  HYDROELECTRIC  PLANTS. 

on  the  teeth.  For  instance,  a  cut  iron  tooth  of  12-inch  face 
and  velocity  of  1000  feet  per  minute  has  a  pressure  per  inch  of 
face  of  125  pounds.  A  similar  tooth  with  velocity  of  600  has 
a  pressure  of  250  pounds.  This,  too,  is  for  gears  running  entirely 
in  oil. 

.  press,  at  pitch  circle  X  vel.  ft.  per  min. 

horse  power  of  one  tooth  =   * 

oo,UUU 

The  pressure  exerted  at  pitch  line  in  pounds  by  one  gear  acting 
on  another  tending  to  produce  rotation,  is  found  thus: 

33,000  X  horse  power 

Vel.  of  tooth  at  pitch  circle  in  ft.  per  min. 

Thus  a  gear  60  inches  in  diameter,  transmitting  100  horse 
power  to  the  pinion,  exerts  at  the  pitch  circle  the  pressure 

33,000X100 


15.70X150 


=  1400  pounds, 


FIG.  434. 

15. 7  being  the  circumference  of  a  5-foot  circle.  All  this  pressure 
is  considered  as  acting  on  a  single  tooth.  In  the  above,  if  the 
tooth  is  10  inches  wide  the  pressure  per  inch  of  tooth  equals 
140  pounds.  This  would  be  a  very  moderate  pressure.  In 
heavy  gears  used  continually  and  where  more  or  less  grit  gets 
into  them,  as  low  a  pressure  as  100  pounds  per  inch  of  tooth  is 
used.  Such  gears  should  be  incased  in  dust  proof  cases  and 
run  in  oil. 

Common  practice  gives  y  =  240  p  b  where  y  is  the  pressure 
on  the  tooth  as  found  above ;  p  the  pitch  and  b  the  breadth  of 
the  tooth  =  ten  inches  in  above  example,  y  =  200  p  b  is  much 
better  practice  for  wear,  p  =  circular  pitch. 

Where  two  or  more  gears  are  placed  on  the  same  shaft  they 
should  be  so  placed  that  they  thrust  in  opposite  directions,  thus 
neutralizing  the  effect.  (See  Fig.  434.) 

For  strength  of  a  gear,  W  =  s  p  f  y,  where  5  =^  values  in  Table 
LIV,  p  =  circular  pitch,  /  =  width  of  tooth,  y  =  the  values 
given  in  the  Table  LV. 


POWER  TRANSMISSION. 


443 


The  width  of  the  tooth  is  generally  2  to  3  times  the  pitch  p, 
but  may  be  greatly  increased  to  reduce  the  pressure  per  inch  of 
tooth.  Thickness  of  the  rim  of  gear  below  root  of  tooth  equals 
depth  of  tooth. 

TABLE  LIV  (Lewis). 
SAFE  STRESS  ON  TEETH  PER  SQUARE  INCH  OF  MATERIAL. 


Velocity  of  teeth   in 
ft.  per  min  

100 

200 

300 

600 

900 

1200 

1800 

2400 

Safe    stress,    s,    cast 
iron  

8,000 

6,000 

5,000 

4,000 

3,000 

2,400 

2,000 

1,700 

Safe  stress,  s,  steel  .  . 

20,000 

15,000 

12,000 

10,000 

7,500 

6,000 

5,000 

4,300 

fSafe  stress,  s,  wood 

5,000 

4,000 

3,000 

2,500 

2,000 

1,500 

1,300 

1,000 

t  Tredgold. 


TABLE  LV. 

VALUES  OF  y. 


No. 
of 
teeth. 

Factor  of  Strength  y. 

No. 
of 
teeth. 

Factor  of  Strength  y. 

Involute 
20° 
obliquity. 

Involute 
15°,  and 
cycloidal. 

Radial 
flanks. 
15° 

Involute 
20° 
obliquity. 

Involute 
15°,  and 
cycloidal. 

Radial 
flanks. 

12 

.078 

.067 

.052 

27 

.111 

.100 

.064 

13 

.083 

.070 

.053 

30 

.114 

.102 

.065 

14 

.088 

.072 

.054 

34 

.118 

.104 

.066 

15 

.092 

.075 

.055 

38 

.122 

.107 

.067 

16 

.094 

.077 

.056 

4.3 

.126 

.110 

.068 

17 

.096 

.080 

.057 

50 

.130 

.112 

.069 

18 

.098 

.083 

.058 

60 

.134 

.114 

.070 

19 

.100 

.087 

.059 

75 

.138 

.116 

.071 

20 

.102 

.090 

.060 

100 

.142 

.118 

.072 

21 

.104 

.092 

.061 

150 

.146 

.120 

.073 

23 

.106 

.094 

.062 

300 

.150 

.122 

.074 

25 

.108 

.097 

.063 

Rack 

.154 

.124 

.075 

It  is  often  advisable  to  calculate  gears  by  diametral  pitch. 
Thus,  if  the  centers  of  two  shafts,  upon  which  it  is  desired  to 
place  different  sets  of  gears  having  varying  ratios,  are  fixed,  use 
diametral  pitch.  Since  diametral  pitch  is  so  many  teeth  per 
inch  of  diameter,  by  selecting  a  distance  between  centers  which, 


444 


HYDROELECTRIC  PLANTS. 


when  multiplied  by  that  diametral  pitch,  will  give  a  whole  num- 
ber, any  desired  combination  of  gears  can  be  used. 

Suppose  the  distance  between  centers  is  26.41  inches  and  the 
diametral  pitch  p'  =  3,  we  have  N  =  p'  X  26.41  X  2  and  N=  156.86 
which  is  not  a  whole  number.  If  the  distance  =  26.33,  we  have 
N  =  158  as  the  number  of  teeth  in  both  gears.  If  the  ratio  of 

168 
the   gears  =  6  to  1    we  have   — ^-  =  28  teeth  in  the  pinion  and 

168  —  28  =  140  teeth  in  the  gear.  Any  ratio  may  be  selected, 
the  only  limitation  being  that  the  sum  of  all  the  teeth  must 
equal  168;  26.66  inches  would  have  worked  out  also.  If  the 
pitch  was  4,  then  26.25,  26.5,  and  26.75  would  have  given  a 
whole  number,  etc. 


FIG.  ±35. 


WORM    AND    GEAR. 

The  worm  and  gear  is  a  construction  which  is  used  where  a 
large  transmission  ratio  is  desired. 

The  best  results  are  obtained  when  the  worm  is  of  hardened 
steel  with  polished  double  or  triple  threads,  and  having  a  ball 
thrust  bearing,  the  gear  being  of  bronze  with  hobbed  teeth,  the 
whole  running  in  a  bath  of  oil.  Involute  teeth  are  best.  Use 
circular  pitches  in  all  calculations.  The  lead  of  a  worm  is  its 
advance  per  revolution.  The  lead  of  a  double  thread  worm 
equals  twice  its  pitch. 


POWER  TRANSMISSION.  445 

To  get  the  strength  consider  thrust  of  worm  as  acting  on  one 
tooth  of  a  length  equal  the  face.  Solve  as  for  other  gears.  The 
proper  proportions  are  as  follows: 

Outside  diameter  of  worm,  single  thread 4xpitch 

Outside  diameter  of  worm,  double  thread 5xpitch 

Outside  diameter  of  worm,  triple    thread 6xpitch 

Face  of   worm  gear  wheel  =  0.75  outside  diam.  of  worm. 

Pitch  diam.  of  gear  wheel  =  (no  teeth  x  pitch)  -j-  n. 

Throat  diam.  of  gear  wheel  =  pitch  diam.  +  2  -=-  diametral  pitch 

Outside  diam.  of  gear  wheel  =  pitch  diam.  +  4  ^  diametral  pitch 

Diametral  pitch  =  ;r-r-  circular  pitch 

Included  angle  of  worm  tooth  =  29° 

Whole  depth  of  tooth  of  worm  or  gear  =   .  687  X  p 

HARNESS. 

That  part  of  the  iron  work  supporting  the  line  shaft  of  the 
turbine  drive,  is  called  the  harness.  The  harness  is  made  up 


FIG.  436. 

of  the  bearings,  bridge-trees  and  the  steel  beams  supporting  the 
bridge-trees.  Commonly  the  bridge-trees  are  made  of  cast 
iron,  though  they  may  be  of  wood  or  steel. 

Fig.  436  shows  a  complete  bridge -tree' of  a  common  type. 
Sometimes  two  /  beams  are  used,  as  shown  to  the  left,  and  at 
others  one. 

Fig.  437  gives  a  view  of  a  pair  of  gears  supported  by  timber 
bridge-trees.  It  will  be  noted  that  the  bearing  A  is  of  necessity 
very  short,  1J  Z>,  but  the  bearing  B  gives  the  necessary  rigidity. 
The  bearing  B  should  be  at  all  times  out  of  water.  This  view 
also  shows  how -the  shaft  is  enlarged  at  the  pinion.  In  this 
case  the  different  turbines  were  thrown  out  of  use  by  simply 
slipping  the  pinion  out  of  gear.  In  Fig  436  two  rods  A  are 


446 


HYDROELECTRIC  PLANTS. 


shown.  These  run  from  bridge-tree  to  bridge-tree  and  tend  to 
steady  the  entire  harness.  All  bearing  should  be  of  the  ball- 
and-socket  ring  oiling  type.  Roughly,  a  bridge- tree  will  cost 
$100,  or  about  4  cents  per  pound  (without  bearings). 


BELTING. 

Modern  practice  is  to  dispense  with  belts  wherever  possible, 
substituting  an  electric,  a  compressed  air  or  a  rope  drive.  How- 
ever, as  they  are  still  used  to  some  extent,  a  briet  treatment  of  the 
subject  will  be  necessary. 

For  steady,  hard  usage  in  dry  places  a  good  leather  belt  is 
preferable  to  all  others.  Leather  belts  will  stand  rubbing, 
such  as  caused  by  crossed  belts,  shifters,  etc.  For  damp 
places  the  rubber  or  gandy  belt  is  used.  The  power  trans- 
mitted by  the  rubber  and  leather  belt  is  about  the  same  for 
the  same  tension. 

Ordinary  belts  will  safely  stand  a  tension  of  45  pounds  per 
inch  of  width  for  single  belt  and  75  pounds  per  lineal  inch  for 
double.  This  tension  is  exerted  at  the  periphery  of  the  pulley 
and  becomes  a  measure  of  the  power  transmitted ;  thus  a  single 
belt  10  inches  wide  runs  over  a  pully  at  a  speed  of  1000  feet  per 
minute,  therefore 

1000x10x45      , 
-33500-  =13-7h'P- 


POWER  TRANSMISSION.  447 

The  longer  the  belt  the  better,  because  a  less  tension  has  to  be 
maintained,  as  the  sag  increases  the  arc  of  contact. 

It  must  be  remembered  that  the  effective  tension  is  the  differ- 
ence between  the  tension  on  the  tight  and  loose  sides  when  run- 
ning with  a  load.  Therefore,  calculate  the  tension  necessary 
to  pull  the  load  and  make  the  tension  on  the  belt  when  idle 
equal  to  the  safe  tension  less  this  effective  tension. 

In  selecting  a  belt  it  must  be  borne  in  mind  that  while  the 
power  transmitted  is  directly  proportional  to  the  tension,  it  is 
often  a  bad  policy  to  get  the  necessary  tension  by  merely  tight- 
ening the  belt  or  taking  up  the  slack.  On  short  spans  it  is  better 
to  get  the  necessary  tension  by  adding  to  the  weight  of  the  belt, 
Fig.  438.  This  increases  the  sag  and  arc  of  contact. 

For  pulleys  over  12  inches  diameter  use  a  double  or  triple 
leather  belt  or  a  correspondingly  heavy  rubber  or  cotton  belt. 
The  latter  when  6  to  7-ply  has  an  effective  pull — 6/7  that  of 
first-class  single  ply  leather. 


FIG.  438. 

Wave  motion  on  the  slack  side  and  running  from  side  to  side 
of  pulley  under  light  loads  is  caused  by  too  thin  a  belt.  This 
wave  motion  wears  out  bearings,  shafting  and  belts.  Avoid 
vertical  belts.  The  angle  should  be  at  least  45  degrees.  Avoid 
such  long  heavy  belts  that  the  allowable  tension  is  exceeded. 
While  the  tensions  given  in  the  tables  are  considered  good 
practice  by  some  of  the  most  reliable  manufacturers,  Taylor 
claims  that  if  half  the  tension  is  used  the  life  will  be  increased 
about  2.6  times.  The  efficiency  will  also  be  increased  and  the 
life  of  the  bearings. 

For  leather  belts  always  place  the  hair  side  of  the  belt  next 
the  pulley  as  so  placed  it  will  transmit  30  per  cent,  more  power 
than  if  the  hair  side  is  placed  outside.  For  narrow  belts  run 
over  small  pulleys  the  distance  between  center  should  be  at 
least  15  feet.  For  larger  belts,  say  6  to  12  inches,  20  to  25  feet 
and  for  the  largest  sizes  25  to  30  feet. 

Whang  leather  lacing  makes   the   best   fastening  especially 


448  HYDROELECTRIC  PLANTS. 

for  small  pulleys,  but  large  belts  should  be  made  continuous 
by  splicing  and  cementing. 

Belts  run  best  at  high  speeds  (not  more  than  5000  feet  per 
minute  for  single  nor  more  than  4000  feet  per  minute  for  double 
leather  belts).  All  belting  should  be  laid  out  so  that  the  slack 
side  of  the  belt  is  on  top,  the  pull  being  on  the  lower  belt. 

The  idler  should  be  placed  as  close  as  possible  to  the  smallest 
pulley  regardless  whether  it  is  the  driver  or  the  driven.  An 
idler  (or  tightener)  is  absolutely  necessary  on  vertical  belts; 
speed  should  not  exceed  5000  feet  per  minute. 

A  splendid  splice  for  rubber  belts  is  that  shown  in  Fig.  439. 
The  surfaces  of  one  end  of  belt  as  a,  a  are  given  a  coat  of  rubber 
dissolved  in  gasoline.  The  surfaces  b,  b  of  the  other  end  are 
coated  with  rubber  dissolved  in  bisulphide  of  carbon.  Place 
in  a  press  till  dry. 


V*  '  is, 


FIG.  439. 

The  horse  power  per  inch  width  is  found  from  the  following 
formula : 

S  k  =  horse  power, 

wherein  5  is  the  speed  in  feet  per  minute  and  k  =  0.001665 
for  single  leather  belts  and  k  =  0.002666  for  double  leather  belts. 

For  special  cases  we  find  the  proper  width  from  the  above 
formula  and  then  multiply  by  the  coefficient  C,  given  in  the 
following: 

Double  horizontal  crossed  belts C  =  1.2 

Single  vertical  open  belts C  =  1.8 

Double  vertical  driver C  =  2.0 

Single  horizontal,  large  driver  to  smal.l  pulleys C  —  1.2 

Double  horizontal,  large  driver  to  small  pulleys C  =  1.3 

Quarter  turn  single  belts (7=1.5 

Quarter  turn  double  belts C  =  1.8 

Large  belts  transmit  power  with  a  loss  of  from  6  to  12  per 
cent.  This  includes  the  loss  in  the  four  bearings  supporting 
the  two  pulleys. 


POWER  TRANSMISSION. 


449 


ROPE  TRANSMISSION. 

Rope  transmission  deserves  a  prominent  place  among  trans- 
mitting devices.  In  cleanliness,  efficiency  and  cheapness  it  is 
much  superior  to  shafting  and  belts.  It  is  adapted  to  the 
lightest  or  the  heaviest  power  transmission. 

MANILLA   HEMP   AND   COTTON   ROPES. 

The  usual  transmission  rope  for  long  distances  is  of  steel  and 
consists  of  six  strands  having  19  wires  to  the  strand.  A  hemp 
core  is  placed  at  the  center  to  give  pliability,  but  for  short  drives 
such  as  could  be  made  with  a  belt  a  number  of  hemp  or  manilla 
ropes  of  three  strands  are  used. 

TABLE  LVI  (C.  W.  Hunt). 
HORSE  POWER  OF  MANILLA  ROPE  AT  VARIOUS  SPEEDS. 


°«u' 

P 

Speed  of  Rope  in  Feet  per  Minute. 

Smallest 
Diam.  of 
Pulley. 

1500 

2000 

2500 

3000 

3500 

4000 

4500 

5000 

6000 

7000 
2.2 

8000 

i 

1.45 

1.9 

2.3 

2.7 

3. 

3.2 

3.4 

•  3.1 

2.2 

0 

20  in. 

I 
i 

2.3 
3.3 
4.5 

3.2 
4.3 
5.9 

3.6 
5.2 
7.0 

4.2 

5.8 
8.2 

4.6 

5.0 

5.3 

4.9 

3.4 

3.4 

0 
0 
0 

24  " 
30  " 
36  " 

9.1 

9.8 

10.8 

9.3 

6.9 

6.9 

1 

5.8 

7.7 

9.2 

10.7 

11.9 

12.8 

13.7 

12.5 

8.8 

8.8 

0 

42  " 

11 

9.2 

12.1 

14.3 

16.8 

18.6 

20.0 

21.4 

19.5 

13.8 

13.8 

0 

54  " 

H 

13.1 

17.4 

20.7 

23.1 

26.8 

28.8 

30.8 

28.2 

19.8 

19.8 

0 

60  " 

11 

18. 

23.7 

28.2 

32.8 

36.4 

39.2 

41.8 

37.4 

27.6 

27.6 

0 

72  " 

2 

23.2 

30.8 

36.8 

42.8 

47.6 

51.2 

54.8 

50.0 

35.2 

35.2 

0 

84  ' 

TABLE  LVII  (C.  W.  Hunt). 
PROPER  SAG  OF  MANILLA  ROPE. 


Distance 
between 
pulleys, 
feet. 

Driving 
side. 

Slack  Side  of  Rope. 

All  speeds. 

80  ft.  per  sec. 

60  ft.  per  sec. 

40  ft.  per  sec. 

40 

4  inches 

7  inches 

9  inches 

11  inches 

60 

10 

17 

20       " 

23 

80 

17       " 

28       " 

34 

39 

100. 

24       " 

44 

53       " 

62       " 

120 

35 

63       " 

75       " 

88       " 

140 

46       " 

86 

105 

117 

160 

60       " 

111 

135       " 

168       " 

450 


HYDROELECTRIC  PLANTS 


TABLE  LVIII. 
PROPER  TENSION  ON  SLACK  PART  OF  ROPE 


Speed  of 
Rope, 
ft.  per  sec. 

Diameter  of  Rope  and  pounds  tension  on  slack  rope. 

1" 

if* 

iy 

11" 

2" 

\ 

8 

4 

s" 

20 

10 

27 

40 

54 

71 

110 

162 

216 

283 

30 

14 

29 

42 

56 

74 

115 

170 

226 

296 

40 

15 

31 

45 

60 

79 

123 

181 

240 

315 

50 

16 

33 

49 

65 

85 

132 

195 

259 

339 

60 

18 

36 

53 

71 

93 

145 

214 

285 

373 

70 

19 

39 

59 

78 

101 

158 

236 

310 

406 

80 

21 

43 

64 

85 

111 

173 

255 

340 

445 

90 

24 

48 

70 

93 

122 

190 

279 

372 

448 

One  or  more  grooves  may  be  used  the  bottom  of  the  groove 
being  lined  with  wood  or  leather  filling  (Fig.  440),  which  lessens 
the  wear  on  the  rope.  The  wood  filling  is  apt  to  get  loose  when 


e'xposed  to  the  weather,  and  even  the  leather  if  left  idle  will 
loosen  up. 

A  filling  consisting  of  alternate  pieces  of  leather  and  rubber 
is  the  best. 


FIG.  441. 


0     0 

~~&ttp. azfy>. 


The  efficiency  of  a  rope  drive  is  quite  high,  being  about  96 
per  cent,  in  a  single  span  drive  and  decreasing  2  per  cent,  for 
each  relay  or  sub-division  of  the  system  as  shown  in  Fig.  441. 

When  several  grooves  are  used  they  may  be  turned  out  of 


POWER  TRANSMISSION. 


451 


the  solid  metal  as  shown  in  Fig.  442,  no  filling  being  used  and 
the  ropes  not  touching  the  bottom.  The  iron  must  be  smooth 
and  free  from  all  flaws. 


TABLE  LIX. 
HEMP  ROPE,  THREE  STRANDS. 


Diameter 
of 
pulley* 
feet". 

Size  of  Rope. 

Strength 

Weight 
per  ft., 
pounds. 

Length 
per  lb., 
feet. 

Diameter, 
inches. 

Circum., 
inches. 

Breaking 
strength,  Ibs. 

Safe 
strength. 

21 

6 

17.1 

324.000 

10,800 

9.4 

.1064 

19 

5i 

15.7 

272,000 

9,070 

7.9 

.1266 

16.5 

5 

14.25 

225,000 

7,800 

6.52 

.1533 

14 

'   4* 

12.1 

182,000 

6,100 

5  28 

.1894 

12 

4 

11.4 

144,000 

4,850 

4.18 

.2392 

11 

3J 

10.7 

126,000 

4,100 

3.67 

.2725 

10 

3* 

10. 

110,000 

3,500 

3.2 

.3125 

9 

3J 

9.27 

95,000 

2,970 

2.76 

.3613 

8 

3 

8.57 

81,000 

2,530 

2.35 

.4255 

7 

21 

7.85 

68,000 

2,100 

1.97 

.5076 

6 

*ft 

7.14 

56,200 

1,800 

1.63 

.6135 

5.25 

2J 

6.43 

45,500 

1,420 

1.32 

.7575 

4.25 

2 

5.70 

36,000 

1,100 

1.04 

.9615 

3.4 

If 

5.10 

27,500 

900 

.80 

1.25 

2.75 

11 

4.28 

20,200 

630 

.588 

1.700 

2.1 

11 

3.97 

14,000 

430 

.407 

2.457 

1.5 

1 

2.86 

9,000 

280 

.261 

3.831 

1.22 

1 

2.5 

6,900 

210 

.200 

5.000 

.97 

I 

2.14 

5,050 

150 

.147 

6.803 

.74 

1 

1.78 

3,500 

100 

.102 

9.803 

.53 
.34 

.18 

i 

1 
1 

1.43 
1.07 
.71 

2,240 
1,260 
560 

75 

.065 
.036 
.016 

15.38 

27.77 
62.5 

The  horse  power  transmitted  by  one  rope  is 
vD2 


II 


825 


where  v  is  the  velocity  in  feet  per  second,  and  D  the  diameter 
of  rope  in  inches. 


452  HYDROELECTRIC  PLANTS. 

The  tension  on  the  slack  rope  when    working  is 


where  7  is  the  tension  due  to  the  transmitting  of  the  power  4- 
the  tension  due  to  the  weight  of  rope;  F  the  centrifugal  force, 

F==  PV* 
~  32.2' 

where  p  is  the  weight  of  one  foot  of  rope  in  pounds  and  v  the 
velocity  of  rope  in  feet  per  second.  The  tension  7,  due  to 
33000  XH 


the  power  is 


V 


•,  when  V  is  the  velocity  of  rope  in  feet 


per  minute.     In   solving  the   above   equation   t  may  be   taken 
from  Table  LVIII  in  finding  7. 


~ c/ ~ 


-«M*j» 


a  - 
e  - 


c  - 
*,  $ 

FIG.  442. 


Table  LVII  gives  the  sag  on  the  slack  side  of  the  rope  to  pro- 
duce the  proper  tension,  or,  the  sag  which  would  be  produced 
by  the  tension  given  in  Table  LVIII. 

The  most  efficient  drives  are  made  with  a  large  number  of 
small  ropes.  A  5/16-inch  rope  running  over  30-inch  sheaves 
is  the  best  for  drives  up  to  20  h.p.,  ^-inch  for  drives  of  from  20 
to  40  h.p.  and  f-inch  for  40  to  80. 

Where  the  sheaves  are  of  different  diameters  the  ropes  do  not 
pull  alike  and  therefore  the  angle  of  the  grooves  on  the  smaller 
pulley  must  be  made  less  so  as  to  get  the  same  friction  on  both 
pulleys.  On  long  out-door  transmissions  the  large  sheaves  re- 
ceive heavy  side  pressures  from  the  force  of  the  wind  and  must 
be  made  strong  laterally. 

It  is  advisable  to  place  idlers  to  support  the  rope  where  on 
account  of  the  space,  the  tension  becomes  excessive. 


POWER  TRANSMISSION. 


453 


STEEL  ROPES. 

Steel  ropes  are  largely  used  for  out-door  work.  The  sheaves 
or  pulleys  are  the  same  as  for  the  soft  ropes  though  they  are 
more  often  without  filling. 

As  in  the  case  of  the  soft  ropes  there  must  be  a  sufficient 
amount  of  friction  between  the  sheaves  and  the  rope  to  prevent 
slipping.  This,  having  selected  the  proper  diameter  of  pulley, 
is  obtained  by  regulating  the  tension  on  the  cable  by  means  of  a 
tail  sheave  and  counter  weight. 

The  coefficient  of  friction,  /,  for  sheaves  is  given  as  follows: 

Dry  Wet  Greasy 

Rope  on  a  grooved  iron  pulley 120  .085  .070 

Rope  on  a  wood-filled  pulley 235  .170  .140 

Rope  on  a  rubber  and  leather  filling 495  .400  . 205 

Then  to  find  the  proper  weight  W  on  the  counter  balance, 

W  =  C  P,  where  P  =  ~    — — ,  is  the  useful  pull  on  the  rope, 

and  C.is  a  constant  depending  on  the  above  values  of  /  and  the 
number  of  ropes,  N,  used.     C  is  given  in  Table  LX. 

TABLE  LX. 
VALUES  OF  C  IN  FINDING  PROPER  COUNTER  WEIGHT. 


N.  Number  of  ropes  used  on  half  laps. 


f. 

1 

2 

3 

4 

5 

6 

.07 

9.130 

4.623 

3.141 

2.418 

1.999 

1.729 

.085 

7.536 

3.833 

2.629 

2.047 

1.714 

1.505 

120 

5.345 

2.777 

1.953 

1.570 

1.358 

1.232 

.140 

4.623 

2.418 

1.729 

1.416 

1.249 

1.154 

170 

3.833 

2.047 

1.505 

1.268 

1.149 

1.085 

.205 

3.212 

1.762 

1.338 

1.165 

1.083 

1.043 

235 

2.831 

1.592 

1.245 

1.110 

1.051 

1.024 

.400 

1.795 

1.176 

1.047 

1.013 

1.004 

1.001 

.495 

1.538 

1.095 

1.019 

1.004 

1.001 

Example:     There  are  400  h.p.  to  be  transmitted;  2-inch  rope; 
speed  of  rope  =  3600  feet  per  minute ; 

33000x400 


3600 


3666  pounds  useful  pull  on  the  rope. 


454  HYDROELECTRIC  PLANTS. 

Find  N,  the  number  of  ropes.  The  actual  horse  power  trans- 
mitted may  be  found  approximately  from 

H  =  3.1D2X*>, 

where  D  =  diameter  of  rope  and  v  =  velocity  in  feet  per  second, 
therefore  H  =  3.1x4x60  =  74.4.  But  we  have  400  h.p.  to 
transmit,  therefore, 

400 

=-7-  -.  =  5  .  37  =  n  ropes. 
74.4 

Taking  6  as  the  proper  number  and  referring  to  Table  LX  for 
a  wet  rope  on  an  iron  pulley,  C  =  1  .505,  W  =  C  P. 

W  =  1.505x3666  =  5517  pounds. 

TABLE  LXI. 
PROPER  DEFLECTION  FOR  WIRE  ROPE. 

Span  in  feet  .............   50        100      150        200         250         300         350  400        450 

Deflection  in  inches  ......  1.75       7        15.5     27.62     42.25     62.25     84.62     110.62     140 

A  less  deflection  than  3  inches  corresponding  to  a  span  of 
54  feet  does  not  give  satisfactory  results. 

The  maximum  tension  on  the  rope  occurs  at  the  ends  and  is 
given  by 


when  p  is  the  weight  of  one  foot  of  rope  ;  /  the  horizontal  distance 
between  pulleys  in  feet,  and  h  the  deflection  given  in  Table  LXI. 
To  this  tension  must  be  added  that  due  to  transmitting  the 
power  or  the  useful  pull,  as  above  found.  The  horizontal  pull 
on  the  pulley  is  the  useful  pull  4-  2  T'.  If  the  tension  Tf  is  the 
W  in  the  above  formulas  there  will  be  no  counter  weight  required, 
and  in  all  cases  the  counter  weight  should  equal  W  minus  T. 

The  sheaves  should  be  of  large  diameter,  as  not  only  does  the 
efficiency  of  the  drive  depend  largely  upon  it,  but  also  the  wear 
of  the  ropes. 

For  ropes  of  7-  wire  strands  the  pulley  should  ha-e  a  diameter 
equal  to  150  D;  for  12  strands,  115  D;  for  19  strands,  90  D, 
D  being  the  diameter  of  the  rope. 


POWER  TRANSMISSION. 


455 


TABLE  LXII. 
HORSE  POWER  OP  WIRE  ROPES. 


Diam. 
of  wheel, 
feet. 

No.  of 
revs.  min. 
of  pulley. 

Diam. 
of 
rope. 

H.P. 

Diam. 
of  wheel, 
feet. 

No.  of 
revs,  per 
min. 

Diam. 
of 
rope. 

H.P. 

3 

80 

i 

3 

7 

140 

A 

35 

3 

100 

i 

3* 

8 

80 

f 

26 

3 

120 

i 

4 

8 

100 

i 

32 

3 

140 

1 

4i 

8 

120 

f 

39 

4 

80 

1 

4 

8 

140 

f 

45 

4 

100 

1 

5 

9 

80 

f 

47 

4 

120 

1 

6 

9 

100 

I 

59 

4 

140 

i 

7 

9 

120 

f 

70 

5 

80 

A 

9 

9 

140 

1 

83 

5 

100 

A 

11 

10 

80 

H 

66 

5 

120 

A 

13 

10 

100 

H 

83 

5 

140 

A 

15 

10 

120 

H 

97 

6 

80 

* 

14 

10 

140 

H 

116 

6 

100 

\ 

17 

12 

80 

f 

96 

6 

120 

i 

20 

12 

100 

f 

120 

6 

140 

* 

23 

12 

120 

I 

145 

7 

80 

A 

20 

12 

140 

I 

173 

7 

100 

A 

25 

14 

80 

H 

145 

7 

120 

A 

30 

14 

100 

1ft 

180 

In  figuring  the  strain  on  the  rope  the  actual  area  of  all  the 
wires  in  the  rope  must  be  taken.  Safe  stress  for  iron  rope  is 
24,640  pounds  per  square  inch. 

Steel  ropes  are  preferable  to  iron.  For  a  long  transmission 
such  as  several  thousand  feet,  select  a  larger  rope  than  the  tables 
call  for  and  run  it  at  a  low  velocity  over  large  sheaves.  Support 
the  ropes  on  large  idlers  every  hundred  feet  or  so.  Such  a  trans- 
mission is  well  suited  to  hydraulic  powers  where  the  factory  is 
some  distance  away  from  the  power  house. 

CARE    OF    THE    ROPES. 

All  steel  or  iron  rope  must  be  frequently  oiled  with  linseed 
oil,  tar  or  any  oil  free  from  acid.  It  should  be  very  carefully 
uncoiled  from  the  shipping  coil  to  avoid  kinks. 


456 


HYDROELECTRIC  PLANTS. 


The  nominal  diameter  of  the  rope  is  the  diameter  of  the  circle 
which  just  encloses  it,  and  this  diameter  must  always  be  given 
in  ordering. 


Hoisting  Ropes 


TABLE  LXIII. 

6  Strands  of  19  Wires  Each. 


Iron.                  Cast-Steel. 

Extra  Strong 

Plow-Steel. 

II               II 

Cast  Steel. 

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1* 

^•S 

g^ 

§.s 

u^ 

'S3- 

o, 
g 

a 

< 

W 

< 

jjj 

< 

* 

< 

s 

< 

£_ 

21 

7* 

8.00 

156,000 

52,000 

312,000 

104,000 

364,000 

121,333 

416,000 

138,667 

I 

2 

61 

•6.30 

124,000 

41,333 

248,000 

82.667 

288,000 

96,000 

330,000 

110,000 

1 

If 

5i 

4.85 

96,000 

32,000 

192,000 

64.000 

224,000 

74,667 

256,000 

85.333 

"to 

H 

5 

4.15 

84,000 

28,000 

168,000 

56,000 

194,000 

64,667 

222,000 

74,000 

I 

it 

4f 

3.55 

72,000 

24,000 

144,000 

48,000 

168,000 

56,000 

192,000 

64,000 

"ij 

11 

41 

3.00 

62,000 

20,667 

124,000 

41,333 

144,000 

48,000 

164,000 

54,667 

^^ 

11 

4 

2.45 

50,000 

16,667 

100,000 

33,333 

116,000 

38,667 

134,000 

44,667 

1/5  "S 

li 

3* 

2.00 

42,000 

14,000 

84.000 

28,000 

98,000 

32,667 

112,000 

37,333 

^H 

i 

3 

1.58 

34,000 

11,333 

C8,000 

22.667 

78,000 

26,000 

88,000 

29,333 

w^1 

1 

2| 

1.20 

26,000 

8,667 

52,000 

17,333 

60,000 

20,000 

68,000 

22,667 

tn   *" 

2 

21 

0.89 

19,400 

6,467 

38,800 

12,933 

44,000 

14,667 

50,000 

16,667 

S 

f 

2 

0.62 

13,600 

4,533 

27,200 

9,067 

31,600 

10,533 

36,000 

12,000 

rt  g 

A 

If 

0.50 

11,000 

3,667 

22,000 

7,333 

25,400 

8,467 

29,000 

9,667 

1/3  o> 

H 

0.39 

8,800 

2,933 

17,600 

5,867 

20,200 

6,733 

22,800 

7,600 

F 

A 

n 

0.30 

6,800 

2,267 

13,600 

4,533 

15,600 

5,200 

17,700 

5,900 

'x 

1 

u 

0.22 

5,000 

1,667 

10,000 

3,333 

11,560 

3,853 

13,100 

4.367 

a 

A 

i 

0.15 

3,400 

1,133 

6,800 

2,267 

8,100 

2,700 

—  f 

f 

0.10 

2,400 

800 

4,800 

1,600 

5,400 

1.800 

~r. 

Tensile  strength 

75,000  to 

150,000  to 

190,000  to 

225,000  to 

of  wire  per  sq.  in. 

90,000  ibs. 

200,000  ibs. 

225,000  ibs. 

275,000  Ibs. 

TABLE  LXIV. 
Bending  Stresses  19- Wire  Rope. 


Diam.  of  Bend. 

6 

8 

10 

12 

14 

16 

18 

20 

22 

24 

26 

Diam.  of  Rope. 

i 

1,801 

1,390 

1,131 

965 

827 

726 

654 

586 

535 

495 

455 

A 

3,308 

2,568 

2,098 

1,774 

1,536 

1,355 

1,212 

1,096 

1,000 

920 

852 

1 

3,776 

3,094 

2,620 

2,273 

2,006 

1,796 

1,626 

1,485 

1,366 

1,265 

tr 

5,351 

4,546 

3,951 

3  494 

3  132 

2  838 

2594 

2  389 

2  214 

i 

6,609 

5,755 

5,096 

4,573 

4,147 

3,793 

3,495 

3,241 

A 

8,337 

7,393 

6,642 

6,029 

5,519 

5,089 

4,721 

I 

11,565 

10,270 

9,237 

8,392 

7,689 

7,095 

6,586 

» 

13,360 

12,027 

10,936 

10,027 

9,257 

8,597 

f 

15,309 

13,932 

12  782 

11  807 

10  971 

7 

21  403 

19  662 

18  183 

16  910 

1 

27  612 

25  707 

U 

35,620 

POWER  TRANSMISSION. 


TABLE  LXIV .—Continued. 


457 


Diam.  of  Bend.j  28 

30 

36 

48  1   60 

72 

84   |   96 

108 

120 

Diam.  01  Rope. 

1 

i 

423 

398 

338 

250 

200 

167 

144 

126 

112 

101 

A 

795 

742 

621 

468 

376 

314 

270 

236 

210 

189 

1 

1,178 

1,102 

924 

698 

561 

469 

403 

353 

314 

283 

A 

2,063 

1,931 

1,620 

1,226 

986 

824 

708 

621 

553 

498 

* 

3,021 

2,829 

2,376 

1,800 

1,448 

1,212 

1,042 

913 

813 

733 

ft 

4,403 

4,125 

3,468;  2,630 

2,118 

1,773 

1,525 

1,338 

1,191 

1,074 

1 

6,145 

5,759 

4,847 

3,680   2,967 

2,485 

2,135 

1,876 

1,671 

1,506 

H 

8,024 

7,524 

6,201 

4,818 

3,886 

3,257 

2,802 

2,459 

2,191 

1,976 

1 

10,245 

9,609 

8,101 

6,165 

4,977 

4,173 

3,591 

3,153 

2,809  2,534 

1 

15,805 

14,835 

12,528 

9,556 

7,724 

6,481 

5,583 

4,886 

4,371 

3,943 

i 

24,047 

22,589 

19,113 

14,614 

11,830 

9,937 

8,566 

7,528 

6,714 

6,059 

H 

33,347 

31  ,347 

26,566 

20,357 

16,500 

13,872 

11,966 

10,523 

9,387 

8,474 

U 

42,036 

35,683 

27,400 

22,239 

18,713 

16,153 

14,209 

12,682 

11,452 

H 

48,109 

37,028 

30,096 

25,350 

21,897 

19,272 

17,209 

15,545 

H 

61,238147,229 

38,436 

32,403 

28,008 

24,662 

22,030 

19,906 

if 

J59,094 

48,152 

40,629 

35,140 

30,957 

27,664 

25,005 

if 

.  .  |74,565 

60,844 

49,919 

44,476 

39,203 

35,048 

31,689 

IX 

90  325 

73,795 

62,379 

54,022 

47,639 

42,606 

38,534 

1  8 

2 

88,409 

74,795 

64,814 

57,183 

51,160 

46,285 

2i 

125,387 

106,265 

92,203 

81,428 

72,908 

66,002 

H 

145,246 

126,185 

111,546 

99,951 

90,540 

Tables  LXIII  and  LXIV  were  calculated  by  Mr.  William  Hewitt, 
and  are  published  here  by  his  permission.  The  original,  with  other  data 
on  wire  ropes,  appeared  in  a  pamphlet  entitled  "Wire  Rope  and  its  Ap- 
plication to  Power  Transmission,"  1901,  issued  by  Trenton  Iron  Com- 
pany, Trenton,  N.  J.,  from  whom  copies  can  be  obtained. 

FRICTION  AND  BEARINGS. 

•  The  coefficients  of  friction  are  designated  by  /,  and  to  get  the 
horse  power  required  to  drive  a  .shaft  against  this  friction,  we 
have : 


H  = 


4112  fWdn 
33,000 


where  W  is  the  total   weight  on  the  journal  in  pounds;  d  the 
diam.  of  journal  in  inches,  n  the  revolutions  per  minute. 

A  journal  carries  10  feet  of  6-inch  shaft  and  a  mortise  gear 
weighing  2400  pounds.  The  shaft  runs  at  150  r.p.m.  and  weighs 
900  pounds,  therefore  W  =  3300  pounds  and  the  horse  power 
lost  is 


41  12x.  2x3300x150 


33,000  '- 

is  here  taken  for  a  mineral  oil  and  16  pounds  pressure  per  square 


458 


HYDROELECTRIC  PLANTS. 


inch,  as  .2.  In  addition  to  the  above  weights  there  may  be 
the  equivalent  weight  of  the  thrust  due  to  the  driving  gear  In 
the  above  example  suppose  500  h.p.  is  transmitted.  .  The  driving 
wheel  is  6  feet  in  diameter  and  the  pinion  4  feet.  There  will 
therefore  be 

500x33,000 


velocity  of  tooth  in  feet  per  min. 

pounds  pressure  against  the  bearing  due  to  this  thrust  or  8760 
pounds.     Adding  this  to  the  weight  of  shaft  and  gear,  we  have 

41 12x. 2x12060x150 


33,000 


4.5  h.p.  lost 


or  about  1  per  cent. 

Thvtrston  gives  the  following  coefficients  of  friction. 


TABLE  LXV. 
VALUES  OF  f. 


Oils. 


Pressures. 


8  Ib.  per  sq.  in. 

161b.persq.  in. 

321b.persq.in. 

48  Ib.per  sq.  in. 

Sperm,  lard, 

neat's  foot,  etc. 

.159  to  .25 

.138  to  .192 

.086  to  .141 

.077  to  .144 

Olive,  cotton-seed,  rape,  etc. 

.16    to  .283 

.107  to  .245 

.101  to  .168 

.079  to  .131 

Cod  and  Menhaden  

.248  to  .278 

.124  to  .167 

.097  to  .102 

.081  to  .122 

Mineral  oils 

.154  to  .261 

.145  to  .233 

.086  to  .178 

.094  to  .222 

Always  place  a  bearing  each  side  of  a  gear.  Allow  no  over- 
hung gear. 

The  standard  size  of  shafting  is  given  in  inches,  halves,  and 
quarters  of  an  inch,  but  in  reality  they  are  1-16-inch  smaller 
than  their  listed  size.  Thus  a  5-inch  shaft  is  actually  4  15-16 
in  diameter. 

For  line  shafts  driving  from  vertical  turbines  at  ordinary  speed 
the  length  of  the  journal  should  be  four  times  the  diameter  of 
shaft.  Where  necessary  three  times  the  diameter  will  do. 

Thurston  gives  the  following  list  of  proper  lubricants  : 

Low  temperature  as  in  rock         j  Light  mineral  lubricating  oils, 
drills  driven  by  compressed  air.  ( 

Very  great  pressures,  low  speed  j  Graphite,  soapstone  and  other 

1      solid  substances. 


POWER  TRANSMISSION.  459 

Heavy  pressures,  low  speed.        j  The    above,    and   lard,    tallow 

(      and  other  greases. 

Heavy  pressures,  high  speed.      (  Sperm-oil   and   heavy   mineral 

(      oils,  castor  oil. 

Light  pressures  and  high  speed.  (  Sperm,  refined  petroleum,  olive 

(      rape,  and  cotton-seed  oil. 

Ordinary  machinery.  TLard,  oil,  tallow  oil,  heavy  min- 

heavy    vegetable 


fLard,  oil,  tal 
•<  eral  oils, 
t  oils. 


Practically  all  bearings  must  be  babited.  Different  work 
requires  different  grades  of  babit.  For  the  bearings  on  turbine 
vertical  and  horizontal  shafts  hard  babit  is  usually  the  best. 


FIG.  443. 

To  babit  the  boxes,  take  the  two  halves  of  the  box  off  the  bridge- 
tree  and  bolt  together  with  a  piece  of  thin  cardboard  B  between 
and  center  a  piece  of  shaft  A,  Fig.  443.  This  shaft  must  be  a 
full  |-inch  smaller  than  the  regular  shaft.  With  clay  or  cement, 
close  up  the  ends  and  form  at  one  end  a  funnel.  Heat  the  whole 
bearing  up  so  that  it  is  so  hot  you  cannot  hold  your  hand  upon 
it.  Heat  the  babit  in  a  ladle  and  pour  quickly.  Now  take  the 
halves  apart,  and  with  a  pean,  hammer  the  babit  evenly  over  its 
surface  to  compress  it  somewhat.  Then  scrape  the  edges  at  C 
so  that  the  bearing  will  come  solidly  together.  Bolt  the  halves 
together  and  place  in  a  lathe  and  bore  out  the  bearing  to  fit  the 
shaft.  Such  a  bearing  will  wear  much  longer  and  run  cooler 
than  the  usual  cheaply  made  affair.  Fig.  444  shows  a  bearing 


460 


HYDROELECTRIC  PLANTS. 


of  good  design.     It  has  a  thrust  collar  and  an  oiling  ring,  also 
dust-proof  ends  which  are  filled  with  carded  wool. 


FIG.  444. 

HIGH  TENSION  ELECTRIC  TRANSMISSION. 

In  high  tension  work  it  becomes  exceedingly  important  to  take 
the  best  possible  care  of  the  line  from   the   time   it   leaves   the 


FIG.  445. 


FIG.  446. 


switch-board.      In  leaving  the  building  care  must  be  taken  to 
so  locate  the  line  that  there  will  be  no   dripping  eaves  over  it. 


POWER  TRANSMISSION.  461 

One  method  is  to  take  the  line  out  through  the  roof,  as  in 
Fig.  445.  This  was  the  plan  adopted  for  the  Missouri  River 
50,000-volt  transmission  plant.  It  has  the  defect  of  being  open 
to  snow  drifts  and  sleet.  A  roof  added  as  in  Fig.  446  would 
serve  as  a  great  protection. 

POLES. 

The  best  practice  to-day  is  to  have  two  separate  and  distinct 
pole  lines  wherever  the  continuous  operation  of  the  plant  is 
considered  of  great  importance.  The  Missouri  River  transmis- 
sion line  is  65  miles  long  and  has  two  pole  lines  the  whole  distance, 
The  pole  lines  should  be  far  enough  apart  so  that  one  line  could 
not  possibly  fall  across  the  other.  Each  line  must  have  a 
cleared  path  wide  enough  so  that  no  tree  or  limb  can  fall  upon  it. 
Highways  should  be  avoided  where  a  private  right  of  way  can 
be  procured,  on  account  of  the  danger  of  the  insulators  being 
thrown  at  or  shot  at  by  passing  boys  and  nimrods.  Wires  pass- 
ing houses  and  play-grounds  are  constantly  being  crossed  by 
kite  strings,  etc.,  and  where  the  line  has  to  pass  such  places 
65-foot  poles  should  be  used. 

The  proper  height  of  the  poles  will  depend  entirely  on  the 
topography  of  the  country,  but  generally  speaking,  outside  of 
towns  and  in  a  clear  field  35-foot  poles  should  suffice.  In  Fig. 
447  is  shown  a  pole  top  used  on  the  50,000-volt  transmission 
referred  to  above,  Fig.  448  being  a  section  of  the  glass  insulator. 
The  pin  is  of  oak  boiled  in  paraffin,  and  it  was  found  that  the  pin 
alone  would  stand  a  pressure  of  50,000  volts.  The  glass  sleeve 
is  to  keep  the  pin  dry. 

Poles  carrying  smaller  wires  than  the  above,  say  Nos.  6  to  2, 
could  be  placed  125  feet  apart.  There  is  a  growing  tendency 
to  place  the  poles  farther  apart  and  make  each  pole  a  more  per- 
fect insulating  medium  and  approaching  more  nearly  the  tower. 
There  are  now  a  number  of  plants  transmitting  over  steel  towers 
placed  several  hundred  feet  apart. 

All  wooden  poles  set  in  earth  should  be  of  good,  sound,  well- 
shaped,  live  cedar  wood,  not  less  than  7  or  8  inches  in  diameter 
at  the  top.  They  should  be  cut  square  at  both  ends  and  stripped 
of  their  bark.  All  knots  should  be  trimmed  off  and  no  pole  should 
have  more  than  one  curve  in  it. 

Standard    specifications    for    cedar    poles,    with    5-inch    tops 


462 


HYDROELECTRIC  PLANTS. 


FIG.  448. 


POWER  TRANSMISSION. 


463 


and  25  feet  long  and  upwards,  are  as  follows:  All  poles 
must  be  cut  from  live  growing  timber,  peeled  and  reasonably 
well  proportioned  for  their  height.  Tops  must  be  reasonably 
sound  and  when  seasoned  must  measure  as  follows:  5-inch  tops 
must  measure  15  inches  in  circumference  ;  6-inch  tops,  18j-  inches; 
and  7-inch  tops,  22  inches.  If  poles  are  green,  fresh-cut  or 
water  soaked,  the  5-inch  tops  must  be  5  inches  plump  in  diam- 
eter; 6-inch  tops  19 J  in  circumference  and  8-inch  tops  22 J  inches. 

TABLE  LXVI. 


Height  of  Pole, 


35  ft.  to  45  ft. 
50  "  55  ' 
60  "  80  ' 


Depth  of  Hole. 


5  feet. 


One  way  sweep  allowable  not  exceeding  one  inch  for  every  5  feet. 
The  part  of  the  pole  in  the  ground  is  not  included  in  measure- 
ments for  sweep.  Butt  rot  in  the  center,  including  small  ring 
rot  outside  the  center  must  not  exceed  10  per  cent,  the  area 
of  the  butt.  Butt  rot  which  plainly  seriously  impairs  the  strength 
of  the  pole  above  ground  is  a  defect.  WinH  shake  is  not  a  defect 
unless  very  unsightly.  Rough,  large  knots,  if  sound  and 
trimmed  smooth  are  not  a  defect. 


W/XWJA 


FIG.  449. 

The  depth  a  pole  should  be  set  in  the  ground  depends  on  many 
conditions,  such  as  character  of  soil,  weight  of  the  wires  sup- 
ported, exposure  to  heavy  winds,  etc.,  but  roughly,  Table  LXVI 
will  give  the  depths  which  meet  average  conditions.  The  part 
of  the  pole  in  the  ground  is,  of  course,  the  first  to  decay,  and 
though  many  methods  have  been  adopted  to  preserve  the  wood, 
there  is  no  definite  knowledge  on  the  subject  yet.  Hot  tar  and 


464 


HYDROELECTRIC  PLANTS. 


carbolineutn  are  sometimes  used.  A  good  plan  to  preserve  the 
poles  from  decay  and  also  to  protect  them  from  grass  fires 
is  shown  in  Fig.  449.  The  hole  is  dug  about  12  inches  larger  in 
diameter  than  the  pole,  the  pole  set  in  place  and  concrete  rammed 
in.  The  concrete  is  mixed  in  a  wagon  fixed  up  especially  for 
the  purpose  (see  Fig.  450) ;  and  the  holes  all  having  been  dug 
a  gang  of  men  go  ahead  and  have  each  pole  ready  by  the  time 
the  concrete  wagon  gets  to  it.  This  plan  adds  about  $1.50  to 
$2  to  the  cost  of  the  pole,  but  more  than  doubles  the  life.  The 


FIG.  450. 

holes  may  be  a  foot  shallower  than  given  in  Table  LXVI,  as  the 
area  of  the  concrete  is  greater  than  that  of  the  bare  pole. 

The  strain  on  one  pole  carrying  a  heavy  transmission  line  and 
tending  to  break  it  off  at  right  angles  to  the  line,  may  amount  to 
as  much  as  4000  pounds,  applied  at  top  end,  though  this  would 
only  be  the  case  where  the  wind  amounted  to  a  gale ;  2000  pounds 
is  usually  taken. 

Cedar  is  rapidly  becoming  exhausted,  and  within  the  last 
five  years  has  almost  doubled  in  price.  It  therefore  becomes 
important  to  find  a  substitute.  Oak  is  stouter  than  cedar,  but 


POWER  TRANSMISSION. 


465 


rots  in  the  ground.  The  setting  shown  in  Fig.  449  protects  the 
pole  from  rot,  and  should  permit  the  use  of  less  durable  woods. 
Fig.  451  shows  a  pole  which  depends  for  its  lateral  support  upon 
three  side  guys  of  galvanized  strand  cable  rather  than  upon  the 
earth.  Such  a  setting  makes  the  installation  of  poles  in  rock 
an  easy  matter,  as  no  holes  have  to  be  blasted.  It  is  especially 
adapted  to  boggy  or  sandy  ground,  and  serves  to  protect  the 
poles  from  prairie  fires,  etc. 

Poles  should  not  be  guyed  to  trees  or  buildings. 

The  average  life  of  poles  when  set  in  the  ground  is  given  below: 


FIG.  451. 

Norway  pine 7  years 

Chestnut 15     " 

Cypress 13     " 

White  cedar 10    " 

By  setting  up  longer  poles  than  actually  necessary  at  the  start 
the  decayed  ends  may  be  cut  off  and  the  reduced  pole  set  in  a 
new  hole,  thus  doubling  the  life.  The  earth  around  the  pole 
must  be  thoroughly  tamped. 

The  number  of  men  required  to  set  up  a  pole  is  given  in 
Table  LXVII  though  the  number  given  may  be  somewhat  re- 
duced in  the  case  of  poles  60  feet  and  over  in  length  by  having 
a  good  derrick  mounted  on  a  wagon  especially  fitted  up  for  the 
purpose. 

Climbing  spikes  are  made  of  9/16  inch  square  iron  9  inches 
long  and  one  man  can  drive  about  200  to  250  per  day. 


466 


HYDROELECTRIC  PLANTS. 


TABLE  LXVII. 
LABOR  REQUIRED  TO  SET  POLES. 


Height  of  Pole. 

No.  men 

required. 

No.  of  poles  set  per 
day  including  digging 

30  feet 
40     " 

6  with 
7     " 

pikes 

18 
13 

60     " 

10     - 

derrick 

70     " 

12     " 

•• 

80     " 

15     " 

• 

This  is  the  age  of  concrete-steel  construction  and  in  no  way 
is  its  application  shown  to  better  advantage  than  in  concrete- 
steel  poles.  Fig.  452  shows  a  35  foot  concrete-steel  pole ;  at  the 
top  is  cored  a  hole  D  to  receive  the  top  pin.  The  gain  for  the 


cross  arm  is  one  inch  deep  and  the  arm  is  bolted  as  shown  in 
detail  A  B.  The  bolt  is  passed  around  the  pole  rather  than 
through  it  to  avoid  touching  the  bars  n.  The  reinforcing  as 
here  shown  consists  of  I"x3"  Kahn  bars,  but  any  other  rein- 
forcing will  make  a  good  pole. 


POWER  TRANSMISSION. 


467 


A  35-foot  pole  costs  about  $20,  depending  on  the  cost  of  the 
concrete,  about  J  yard  being  required.  A  45-foot  pole  will 
cost  about  $45. 

Such  a  pole  will  stand  a  greater  transverse  strain  than  will 
cedar  pole  and  will  last  indefinitely;  2000  pounds  horizontal 
pull  at  the  top  is  usually  allowed  for  large  poles. 


FIG.  453. 

Frequently  rivers,  ravines  or  even  bays  have  to  be  crossed 
with  the  transmission  line,  in  which  case  the  pole  becomes  a 
tower.  The  tower  shown  in  Figs.  453  was  built  to  carry  four 
J-inch  cables  over  a  span  of  6200  feet.  The  tower  shown 


468 


HYDROELECTRIC  PLANTS. 


is  65  feet  high  and  the  one  at  the  other  end  is  225  feet  high. 
Fig.  454  shows  one  of  the  four  saddles  carried  on  each  tower. 


Each  layer  fastened  with. 


FIG.  454. 

Fig.  455  shows  the   insulating   link  connecting  the  anchor   and 
the  cable,  there  being  two  connected  to  each  cable. 


POWER  TRANSMISSION. 


469 


The  oil  shown  in  Fig.  455  is  for  the  purpose  of  keeping  the 
micanite  in  a  good  state  for  insulation,  it  having  been  found 
to  deteriorate. 

A  span  of  500  feet  over  a  river  was  successfully  accomplished 
by  bringing  the  wires,  No.  1,  a  complete  turn  over  an  8xlO-inch 
timber,  properly  supported  as  in  Fig.  456.  Each  of  the  four 
anchors  is  built  on  suspension  bridge  principles  and  resists  a 
pull  of  12  tons.  The  cables  have  a  conductivity  equal  to  No. 


FIG.  455. 

2  copper,  weigh  7080  pounds  each,  and  have  a  sag  100  feet  and 
have  a  breaking  stress  of  98,000  pounds.  The  voltage  used  is 
60,000. 

The  same  principle  may  be  carried  out  for  smaller  spans, 
building  the  towers  of  timber  and  using  less  massive  insulators. 

On  account  of  wind  pressure  and  added  strain  due  to  the 


FIG.  456. 

falling  of  one  or  more  poles,  it  is  necessary  to  thoroughly  brace 
up  the  line.  Also  at  every  turn  of  the  line  the  corner  pole  must 
be  well  braced.  On  straight  transmission  line  work  every 
eighth  pole  should  be  thoroughly  guyed.  The  rule  is  to  allow 
50  poles  to  the  mile,  the  extra  6  or  10  poles  serving  for  bracing 
and  anchors.  If  the  poles  are  of  the  type  shown  in  Fig.  451 
this  will,  of  course,  be  unnecessary. 

At  the  end  of  a  line  the  poles  should  be  guyed  as  in  Fig.  457, 
slack  being  left  in  the  proportion  shown,  so  that  only  a  part  of 


470 


HYDROELECTRIC  PLANTS. 


the  strain  comes  on  any  one  of  the  poles.  The  dead  men  A 
(see  Fig.  457)  are  usually  slanted  in  the  direction  of  the  guy 
unless  the  soil  is  very  hard. 

There  are  several  patent  anchors  on  the  market,  which  are 
simply  driven  into  the  ground  and  expanded  in  place.  A  post 
hole  auger  may  be  used  for  sinking  anchors. 


FIG.  457. 


CROSS   ARMS. 

Cross  arms  may  be  of  yellow  pine,  white  oak,  creosoted 
white  pine,  chestnut  or  any  other  first-class  wood. 

For  ordinary  lighting  lines  the  dimensions  vary  from  30 
inches  long,  3Jx4|-inches  section,  for  2-4-pin  arms  to  8  feet 
long,  3fx4f  inches  to  4x5-inches  section,  for  6-8-pin  arms. 

They  are  fastened  to  the  pole  by  means  of  two  -J-inch  to 
f-inch  bolts  or  lag  screws  and  gained  into  the  pole  J-inch. 

All  arms  of  more  than  4  pins  must  be  braced  with  flat  iron 
braces  not  less  than  14"xjx27"  bolted  to  the  cross  arm  with 
•f-inch  carriage  bolts  and  the  two  ends  fastened  to  the  pole 
with  4"xf"  lag  screw. 

On  very  high  tension  transmission  lines  these  braces  are 
sometimes  made  of  wood,  see  Fig.  447. 

A  general  practice  on  transmission  lines  is  to  give  the  arms 
a  thorough  dipping  in  hot  asphaltum  compounds,  sometimes 
a  coating  J-inch  thick  being  obtained.  This  is  applied  after 
the  wood  has  been  well-seasoned  and  helps  to  prevent  a  break- 
down should  an  insulator  give  out.  Boiling  the  arms  in  linseed 
oil  is  also  a  good  plan. 

Cross  arms  should  be  placed  so  as  to  alternately  face  each 
other  on  adjacent  poles  and  be  back  to  back  on  the  next  two. 
This  is  to  add  safety  to  the  bolts  should  several  wires  break 
or  a  pole  fall. 


POWER  TRANSMISSION. 


471 


Double  cross  arms,  that,  is  one  on  each  side  of  the  pole  must 
be  placed  at  all  abrupt  changes  in  direction  and  on  all  end 
poles. 

PINS. 

Pins  should  be  made  of  the  very  best  material  and  are  made 
of  oak  or  locust  or  iron. 

If  oak  is  used  it  must  be  well  boiled  in  paraffin  or  linseed 
oil  else  they  will  decay  inside  of  six  or  eight  years.  On  the 
Missouri  River  transmission  line,  see  Fig.  448,  the  pin  is  de- 
pended on  to  a  certain  extent  for  insulation. 

All  pins  should  be  bolted  into  the  cross  arm  as  in  Fig.  447 


FIG.  458. 


especially  when  the  line  passes  over  very  hilly  country,  as  other- 
wise a  pole  may  be  placed  between  two  more  lofty  ones  in  which 
case  there  is  a  tendency  to  pull  the  pin  out  of  its  socket.  If 
nailed,  the  moisture  which  collects  around  the  pin  will  soon 
rust  the  nail  off.  The  cost  of  the  pin  shown  in  Fig.  448  is 
about  25  cents. 

INSULATORS. 

In  selecting  the  proper  insulators  it  is  sometimes  hard  to 
choose  between  glass  and  porcelain.  Glass  is  transparent, 
which  enables  internal  defects  to  be  detected  and  renders  the 
cavities  undesirable  tenements  for  insects.  It  does  not  present 
a  very  good  mark  to  the  small  boy  and  lunatic.  It  is  cheaper 
than  porcelain.  On  the  other  hand  porcelain  may  now  be 
obtained  in  dull  colors  which  do  not  attract  the  eye.  They 


i72  HYDROELECTRIC  PLANTS. 

may  be  chipped  by  bullets  or  stones  without  being  entirely 
disabled.  It  is  stronger  than  glass  and  less  hydroscopic.  How- 
ever, in  actual  practice  both  glass  and  porcelain  have  been 
used  with  good  success. 


r 


FIG.  459. 


FIG.  460. 


On  the  40,000  volt  Provo  transmission  line,  a  glass  insulator  is 
used  over  105  miles  of  line,  see  Fig.  459. 

The  Edison  Electric  Company's  83  mile,  23,000  volt-line 
uses  a  porcelain  insulator  of  about  the  same  size  as  the  glass 
one  used  in  tne  Provo  system,  and  there  seems  to  be  much  less 


FIG.  461. 

leakage  of  current.  Much  may  be  said  for  and  against  either 
glass  or  porcelain,  but  in  view  of  the  increased  experience 
in  porcelain  manufacturing  and  the  superior  satisfaction  now 
procured  it  is  the  author's  opinion  that  porcelain  is  much  the 
better  for  high  tension  work. 


POWER  TRANSMISSION. 


473 


Porcelain  insulators  are  made  white  or  chocolate  colored,  the 
latter  being  preferred  on  account  of  being  less  conspicuous. 

For  all  ordinary  pressures  up  to  2000  volts  it  might  be  well, 
on  account  of  cheapness,  to  use  a  glass  double  petticoat  insu- 
lator, something  like  Fig.  460.  These  cost  $40  per  thousand. 


FIG.  462. 

For  potentials  between  2000  and  5000,  a  glass  insulator 
having  more  petticoats  as  in  Fig.  461,  costing  about  $55  per 
thousand  should  be  used. 

For  higher  voltages,  all  things  considered,  porcelain  should 


FIG.  463. 

be  used.  These  larger  porcelain  insulators  are  made  in  two 
or  more  parts  so  as  to  avoid  large  pieces  of  porcelain,  which 
could  not  be  vitrified  properly.  These  parts  are  fastened  to- 
gether by  means  of  sulphur  (Fig.  458).  Frequently  a  combina- 


474 


HYDROELECTRIC  PLANTS. 


tion  of  glass  and  porcelain  is  used  as  in  Fig.  462,  made  by  the 
Locke  Company.  A  porcelain  insulator  about  10  inches  high 
and  9  inches  in  diameter,  good  for  30,000  to  40,000  volts,  costs 
$500  to  $750  per  thousand. 

The  R.  Thomas  &  Company  of  East  Liverpool,  O.,  make  a  good 
line  of  insulators,  one  of  which  is  shown  in  Fig.  463.  This 
particular  insulator  was  tested  to  120,000  volts,  it  weighs  23 
pounds  and  costs  about  $2500  per  thousand. 

The  common  rule  is  to  test  the  insulator  with  twice  its  work- 


FIG.  464. 


ing  voltage,  that  is,  it  is  given  a  factor  of  safety  of  2,  which 
is,  for  a  three-phase  line,  equivalent  to  a  factor  of  3  between 
the  wire  and  earth. 

It  is  a  good  plan  to  adapt  the  insulator  to  the  conditions 
peculiar  to  the  location  even  if  a  special  design  is  required. 
The  makers  of  the  best  insulators  announce  that  they  are  ready 
to  make  insulators  from  designs  furnished  by  the  engineers. 

In  Fig.  464  is  shown  the  Niagara  type  used  for  a  11,000-volt 
transmission ;  the  one  at  the  left  is  the  old  one  and  the  one  at 
tl:e  right  is  the  new  one. 


POWER  TRANSMISSION.  475 

THE   LINE. 

Transmission  lines  are  frequently  made  of  medium  hard  drawn 
copper  or  aluminium,  though  a  large  proportion  are  of  hard- 
drawn  copper.  This  latter  has  a  breaking  tensile  strength  of 
from  60,000  to  70,000  pounds  per  square  inch,  and  while  the 
conductivity  is  from  2  to  4  per  cent,  less  than  the  annealed, 
and  somewhat  difficult  to  string  up  without  injury,  it  is  to  be 
preferred.  If  the  wires  are  larger  than  No.  1  or  0,  it  is  best  to 
use  a  stranded  hard-drawn  cable  as  it  will  be  more  flexible  and 
is  especially  adapted  to  alternating  current  work. 

Aluminium  has  not  been  generally  adopted  yet,  though  there 
are  some  very  important  transmissions  using  it.  It  at  first 
proved  to  be  unreliable  and  is  still  difficult  to  solder.  It  has 
some  very  valuable  features,  however.  It  is  cheaper  than 
copper  for  the  same  conductivity  and  is  1.3  times  larger  in 
diameter  than  copper,  and  half  as  heavy. 

Its  tensile  strength  should  not  be  taken  at  more  than  15,000 
to  17,000  pounds  per  square  inch.  This  increase  in  size  of 
aluminium  wire  over  copper  would  be  a  disadvantage  were  it 
not  for  the  fact  that  the  larger  the  wires  the  less  the  leakage 
between  them. 

Were  it  not  for  the  low  tensile  strength  and  added  area  ex- 
posed to  wind  pressure,  the  poles  could  be  separated  more  for 
aluminium  than  for  copper,  but  owing  to  these  facts  the  same 
spacing  is  used  in  both  cases.  However,  the  strain  is  much 
less  on  the  insulators. 

All  aluminium  transmission  wires  must  be  stranded  to  insure 
against  breaking.  All  fastenings  must  be  especially  solid  to 
prevent  slipping  as  it  wears  rapidly.  Wherever  aluminium  is 
joined  with  any  other  metal  as  solder,  etc.,  it  must  be  covered 
with  a  waterproof  covering  as  otherwise  a  galvanic  action  will 
be  set  up  which  would  soon  destroy  the  joint.  The  Mclntyre 
joint  is  one  of  the  best  for  this  purpose.  It  consists  of  a  tube 
slipped  over  the  wires  and  then  twisted  together  by  means  of  a 
special  tool. 

For  long  transmission  allowance  has  to  be  made  for  the 
added  electric  capacity  of  aluminium  wires,  being  about  5  per 
cent,  more  than  for  copper. 

A  smaller  copper  wire  than  No.  5  should  not  be  used  for 
transmissions  on  account  of  its  lack  of  strength. 


476 


HYDROELECTRIC  PLANTS. 


On  transmission  lines  the  wires  are  strung  in  the  top  of  the 
insulators  in  which  case  they  are  fastened  as  shown  in  Fig.  464 
However,  on  the  smaller  side  lines  they  are  tied  to  the  side  as 
in  Fig.  465.       When  a  series    tap  is  taken  off,  the    connections 
are  as  shown  in  Fig.  466. 

In  certain  localities  the  wires  have  to  be  insulated  with  some 
continuous  covering.  This  consists  of  an  insulating  compound 
and  a  protective  covering.  The  best  insulation  has  for  the 
first  covering  some  rubber  composition  and  for  the  outer  a 


moist 


FIG.  465.  FIG.  466. 

hard    cotton   braid.     If   the   wire    is   to   be    continually 
gutta-percha  is  better  than  rubber. 

The  length  of  wire  on  a  long  transmission  must  be  carefully 
figured  as  the  sag  between  poles  amounts  to  considerable  amount. 
The  length  L  (Fig.  467)  between  two  poles  A  and  B  is 

Sd2 


L  = 

and  d  = 


H  +  -. 

H2  W 

8  T 


where  d  is  the  sag  in  feet,  at  middle  of  span,  H  the  span  from 
A  to  B  in  feet,  T  the  tension  in  pounds  in  wire  at  C  and  W  the 
weight  in  pounds  of  wire  per  foot. 


FIG.  "467. 

Due  allowance  must  be  made  for  changes  in  temperature,  the 
tension,  of  course,  being  greatest  in  cold  weather.  From  Table 
LXVIII  it  will  be  seen  that  if  a  wire  is  being  strung  between 
poles  100  feet  apart,  when  the  temperature  is  80  degrees  Fahren- 
heit, and  give  it  a  sag  of  If  feet,  the  sag  will  only  be  .158  feet 
When  the  temperature  falls  to  —  10  degrees  Fahrenheit.  Then 

H2  W 

the  tension  at  that  temperature  and  sag  may 


from  T  = 
be  found. 


Sd 


POWER   TRANSMISSION. 


477 


In  Table  LXVIII.  the  column  under  the  -  10°  F.  gives  this 
sag  when  the  wire  is  under  a  tension  of  30,000  pounds  per  square 
inch,  which  is  only  allowing  a  factor  of  safety  of  2  for  medium 
hard  drawn  copper.  It  should  be  4  as  the  tension  T  is  directly 
proportional  to  the  sag  d.  In  the  above  case,  by  doubling  the 
sag,  the  desired  factor  of  safety  will  be  obtained.  Allowance 
must  be  made  for  an  added  weight  of  sleet  and  wind  which 
together  may  add  20  to  30  pounds  to  the  total  weight  per  wire. 
A  telephone  is  more  than  a  luxury  to  a  power  station  and 
should  be  one  of  the  first  things  provided  for.  It  is  also  of 

TABLE  LXVIII. 
TEMPERATURE  IN  DEGREES  F. 


Span 
in 
teet. 

-10° 

30° 

40° 

50° 

60° 

70° 

80° 

90° 

100° 

Deflection  in  Feet. 

50 

.041 

.5 

.666 

.75 

.75 

.833 

.916 

.916 

1 

60 

.0583 

.666 

.833 

.916 

.916 

1.00 

1.083 

1.083 

1.166 

70 

.0833 

.833 

.916 

1.00 

1.083 

1.166 

1.25 

1.25 

1.41 

80 

.100 

.916 

1.083 

1.166 

1.25 

1.33 

1.41 

1.5 

1.58 

90 

.133 

1.083 

.166 

1.33 

1.41 

1.5 

1.58 

1.66 

1.75 

100 

.158 

1.166 

.33 

1.41 

1.58 

1.66 

1.75 

1.92 

2.00 

110 

.192 

1.33 

.5 

1.58 

1.75 

1  .83 

2.00 

2.08 

2.18 

120 

.233 

1.41 

.58 

1.75 

1.83 

2.00 

2.18 

2.25 

2.33 

140 

.308 

1  .66 

.92 

2.08 

2.25 

2.33 

2.50 

2.66 

2.75 

160 

.408 

1.92 

2.18 

2.33 

2.50 

2.66 

2.83 

3.00 

3.16 

180 

.516 

2.18 

2.41 

2.66 

2.83 

3.08 

3.25 

3.42 

3.58 

200 

.641 

2.58 

2.75 

3.00 

3.16 

3.42 

3.58 

3.75 

4.00 

great  value  during  construction.  The  telephone  line  may  be 
strung  on  the  transmission  pole  line.  It  will  then  also  serve 
as  a  leakage  detector,  as  any  great  amount  of  leakage  or  a 
cross  may  be  heard  in  the  .receiver. 

In  running  the  telephone  lines  on  the  transmission  pole  line 
the  transpositions  are  sometimes  made  by  placing  brackets  on 
the  poles  with  both  brackets  on  the  same  side  of  the  pole,  and 
at  transpositions,  placing  the  brackets  on  opposite  sides  of  the 
pole,  as  in  Fig.  468,  one  of  the  brackets  being  made  long  in  the 
sketch  simply  to  indicate  the  upper  bracket,  and  shows  how 
the  upper  wire  is  brought  down  under  the  bracket  on  the  pole 
to  the  left. 


478  HYDROELECTRIC  PLANTS. 

These  transpositions  should  be  made  about  once  to  the  mile 
on  short  lines  and  say  six  to  eight  times  for  the  full  length  on 
longer  ones.  A  very  common  way  is  to  provide  a  two-pin  arm 
for  the  telephone  line  and  use  a  double  type  two-groove  insula- 
tor at  the  transpositions.  A  No.  6  Bell  lightning  arrester  should 
be  installed  at  each  end  of  the  line,  though  not  absolutely  nec- 
essary. 

The  greater  the  distance  between  the  wires  the  greater  the 
induciiion  and  therefore  the  greater  the  drop  in  voltage.  There 
are,  however,  good  reasons  why  the  wires  should  be  as  far 
apart  as  possible.  Birds  frequently  fly  into  the  wires,  especially 
owls;  therefore  if  the  wires  are  several  feet  apart,  the  wings 
of  the  birds  cannot  span  them.  In  the  West  great  trouble  was 
experienced  from  cranes  alighting  on  the  wires,  so  that  a  dis- 
tance of  from  six  to  seven  feet  was  found  necessary  between 
wires. 


FIG.  468. 

Sticks  are  often  thrown  across  the  wires,  but  if  they  are  far 
enough  apart  it  would  take  such  a  heavy  stick  that  it  could  not 
be  successfully  thrown  up  to  the  line.  The  farther  the  wires 
are  apart  the  greater  may  be  the  sag  and  therefore  there  will 
be  less  strain  on  the  wires  and  insulators.  The  farther  the  wires 
are  apart  the  less  will  be  the  leakage  across  the  intervening  air. 

It  is  well  to  calculate  the  inductive  drop  or  inductive  react- 
ance, as  it  is  called,  of  the  line,  due  to  the  spacing  of  the  wires, 
where  the  distance  is  unusually  great. 

The  following  method  of  calculating  the  line  losses  for  alter- 
nating currents  was  given  in  the  American  Electrician  of  June, 
1897,  and  as  it  takes  into  account  the  different  spacing  of  the 
transmission  wires,  it  is  given  here. 

EXAMPLE. — Power  to  be  delivered  to  the  consumer  is  250,000 
watts;  e.m.f.  at  the  consumer's  end  of  the  line  is  2000  volts; 
distance  of  transmission,  10,000  feet;  distance  between  wires  is 
18  inches. 


POWER  TRANSMISSION.  479 

To  start  with,  assume  the  size  of  wire  as  No.  0.  The  power 
factor  is  .80,  and  the  frequency  60  cycles  per  second,  or  7200 
alternations  per  minute  single -phase. 


orrj  000 

-  =  312,500  apparent  watts  to  be  delivered. 


31 9  500 

=  156.25  amperes  (current  in  each  wire). 


From  Table  LXIX,  under  the  heading  18  inches  and  corre- 
sponding to  a  No.  0  wire,  we  find  .228.  Then  we  have,  156.25 
X10X.228  =  356.3  reactance  volts.  This  amounts  to  17.8 
per  cent,  of  the  2000. 

From  the  column  headed  resistance  volts,  we  have  for  a 
No.  0  wire  and  18  inch  spacing,  .197.  Therefore  we  have 
156.25 X  10 X.  197  =  307.8  as  the  resistance  volts  lost.  This  is 
15.4  per  cent,  of  the  2000  volts. 

Now  referring  to  the  curves,  Fig.  469,  we  follow  up  the  ver- 
tical .8  to  the  first  circle.  At  this  point  lay  off  the  resistance 
volts  in  a  horizontal  direction  to  the  right.  From  the  end  of 
this  horizontal  line  thus  laid  off  erect  a  perpendicular  equal  to 
the  reactance  volts  lost.  In  this  case,  as  shown,  the  top  of  the 
vertical  comes  nearly  to  the  circle  denoting  a  drop  of  24  per 
cent.  Therefore  the  drop  in  terms  of  the  generator  e.m.f.  is 


We  have  found  the  resistance  volts  to  be  307.8  and  the  cur- 
rent to  be  156.25  amperes.     Hence  the  power  lost  307.8  X  156.25 

=  48.1  kw.     The  per  cent,  loss  is  —-  -  -—  r  =  16.1  per  cent. 

.  1 


For  two  and  three  phase  transmissions  find  the  current  in 
the  conductors  as  in  the  following  method  (General  Electric) 
and  proceed  as  in  the  above  example. 


480 


HYDROELECTRIC  PLANTS, 


V 

POWER 


FIG.  469, 


POWER  TRANSMISSION. 


481 


TABLE  LXIX. 
DROP  DUE  TO  INDUCTIVE  REACTANCE. 


1 

•J 

+J'~H  2 
'3 

resistance  volts 
per  1000ft.  pole 
line.  For  1  amp. 

Rea 

(\ 

be 

stance  volts  per  IOC 

(0  ft.  of  pole  line  for  one  ampere 
200  cycles  per  min.  for  distances 
given. 

/mean  square).     7 
tween  conductors 

¥ 

1" 

2" 

3" 

6" 

9" 

12" 

18" 

24" 

30" 

36" 

0000 

639 

.098 

.046 

.079 

.111 

.130 

.161 

.180 

.193 

.212 

.225 

.235 

.244 

000 

507 

.124 

.052 

.085 

.116 

.135 

.167 

.185 

.199 

.217 

.230 

.241 

.249 

00 

402 

.156 

.057 

.090 

.121 

.140 

.172 

.190 

.204 

.222 

.236 

.246 

.254 

0 

319 

.197 

.063 

.095 

.127 

.145 

.177 

.196 

.209 

.228 

.241 

.251 

.259 

1 

253 

.248 

.068 

.101 

.132 

.151 

.183 

.201 

.214 

.233 

.246 

.256 

.265 

2 

201 

.313 

.074 

.106 

.138 

.156 

.188 

.206 

.220 

.238 

.252 

.262 

.270 

3 

159 

.394 

.079 

.112 

.143 

.162 

.193 

.212 

.225 

.244 

.257 

.267 

.275 

4 

126 

.497 

.085 

.117 

.149 

.167 

.199 

.217 

.230 

.249 

.262 

.272 

.281 

5 

100 

.627 

.090 

.121 

.154 

.172 

.204 

.223 

.236 

.254 

.268 

.278 

.286 

6 

79 

.791 

.095 

.127 

.158 

.178 

.209 

.228 

.241 

.260 

.272 

.283 

.291 

7 

63 

.997 

.101 

.132 

.164 

.183 

.214 

.233 

.246 

.265 

.278 

.288 

.296 

8 

50 

1.260 

.106 

.138 

.169 

.188 

.220 

.238 

.252 

.270 

.284 

.293 

.302 

A  few  years  ago  it  was  thought  good  engineering  to  allow  a 
loss  of  10  per  cent  or  more  in  transmissions,  but  to-day  a  5  per 
cent,  loss  on  full  load  is  the  general  rule  for  all  but  extremely 
long  transmissions. 

This  small  loss  is  made  possible  by  selecting  high  voltages 
an  empirical  rule  being  to  use  1000  volts  per  mile  approximately. 
Of  course  there  are  often  other  considerations  which  enter  to 
influence  the  selection  of  voltage. 

The  wiring  formulas  here  given  are  about  the  simplest  and  most 
exact  of  any  and  are  in  the  form  .gotten  out  and  used  by  the 
General  Electric  Company.  They  may  be  used  to  determine 
the  size  of  copper  conductors,  volts  loss  in  lines,  current  per 
conductor,  and  weight  of  copper  per  circuit  for  any  system  of 
electrical  distribution. 


Area  of  conductor,  circular  mils  = 


DXWXC 
PXE2 


Volts  loss  in  lines  = 


PXEXB 
100 


482 


HYDROELECTRIC  PLANTS. 


Current  in  main  conductors  =  — - —  =  / 


Lbs.  copper 


PXE2X  1,000,000 


W  =  Total  watts  delivered. 

D   =  Distance  of  transmission  (one  way)  in  feet. 

P   =  Loss  in  line  in  per  cent,  of  power  delivered,  that  is  of  W 

E    =  Voltage  between  main  conductors  at  receiving  or  con- 
sumer's end  of  circuit. 

For  continuous  current  C  =  2160,  7=1,5  =  1,  and  A  =  6.04. 
Table  LXX  gives  values  of  the  constants  Ct  T,  B  and  A  when 
applied  to  a.  c.  calculations. 


FIG.  470. 


FIG.  471, 


Vfce  formulas  are  applicable  to  direct  and  alternating  cur- 
rent systems,  and  may  be  used  to  find  the  size  of  wire  to 
transmit  any  amount  of  power  to  any  kind  of  load  known  to 
electrical  engineering. 

In  all  alternating  current  transmissions  the  wires  should  be 
transposed  at  equal  intervals,  and  be  placed  equidistant  from 
one  another,  to  equalize  the  inductive  drop  in  the  phases. 
Many  transmissions  have  the  wires  36  inches  apart,  though  a 
greater  distance  is  sometimes  to  be  recommended. 

The  two  circuits  of  a  quarter  phase  must  be  arranged  as  in 
Fig.  470  or  Fig.  471. 

Fig.  471  shows  the  two  circuits  side  by  side  though  they  may 
be  above  each  other  or  in  any  position  if  that  position  is  main- 
tained. 

The  three  wires  of  a  three-phase  transmission  must  be   ar- 


POWER  TRANSMISSION. 


483 


B 


6,0 

^5 

jS| 

H 

i 

o 


<-H  10 

^H     Ifl 


So  o 
X   X 

S!  2  2 


<  O 


=  99 

CO    (N    O5 


H  H 


NT. 
CTO 


PE 
OW 


O         tr 
X 

CO    <N    (N    (M 


8  S  S  S 


2  2  8  8  S 


NT. 
CTO 


SS8SS2S&8888888 


PER  CENT. 
ER  FACTOR 


g 


'3  oOS  W 

000  1  -I3d 


S5S  28888  8  888888 


22888888888  8" 


§8888888 


punoj   "ij  000'  T  J3d 


3JIAV  B9.IV 


OX<NOJCCOO>CO 
Tj*oO^iOOiO<N 


^OSO^COCOC^C^OCO 


'ON 


484 


HYDROELECTRIC  PLANTS. 


ranged  either  as  in  Fig.  472  or  Fig.  473.  Fig.  472  is  the  best 
and  most  common  method.  In  Fig.  473  the  wires  are  all  on 
one  cross  arm  and  there  are  two  transpositions  as  shown  on 
the  pole  line.  A  quarter-phase  three-wire  line  need  not  be 
transposed. 

For  very  long  transmissions  of  a  hundred  miles  or  more, 
special  calculations  are  necessary  to  find  the  inductive  drop 
which  for  a  circuit  of  100  amperes,  at  60  cycles  transmitted 
200  miles  might  be  50  per  cent. 


•  3 


•  2 


FIG.  472. 


FIG.  473. 


LIGHTNING   PROTECTION. 

Lightning  is  the  most  persistent  foe  to  the  transmission  line 
and  must  be  well  .guarded  against. 

The  best  protection  is  to  provide  the  arresters  and  the  power- 
house equipment  with  choke  coils.  Choke  coils  are  somewhat 
expensive  but  give  splendid  protection.  On  a  long  line  the 


FIG.  474. 

arresters  should  be  most  numerous  near  the  ends  of  the  line. 

The  grounds  connecting  the  arresters  to  earth  must  be  well 
made  else  the  efficiency  of  the  protection  is  greatly  impaired. 
A  galvanized  1^-inch  gas  pipe  driven  five  or  six  feet  into  moist 
ground  will  answer  the  purpose  for  the  arresters  out  on  the  line, 
but  for  those  protecting  the  stations  connections  should  be 


POWER  TRANSMISSION.  485 

made  to  steel  penstocks,  water  pipes,  or  some  such  thoroughly 
grounded  device.  In  the  absence  of  these,  a  large  sheet  of 
galvanized  iron  should  be  buried  in  moist  earth  and  the  ground 
wire  well  soldered  across  it.  The  ground  wire  must  run  as  di- 
rectly as  possible  to  the  earth  plate  and  any  complete  turn  in 
it  will  be  fatal  to  the  protection. 

Fig.  474  shows  a  pole  line  protected  by  barbed  wire  such  as 
is  used  for  fencing.  This  plan  has  been  quite  generally  adopted 
in  the  west;  that  shown  is  in  Canada.  Frequently  the  barbed 
wire  is  fastened  to  the  arm  by  means  of  staples,  though  this  is 
bad  practice  as  the  wire  breaks  at  the  staple. 

Common  glass  insulators  should  be  used.  A  liberal  sag  must 
be  allowed  to  keep  the  tension  down  to  a  safe  figure. 

GENERAL   REMARKS. 

From  the  foregoing  the  following  observations  "are  drawn: 

All  pole  fittings  should  be  of  galvanized  iron. 

All  guy  wires  should  be  of  at  least  two  No.  8  wires  twisted 
together;  for  high  tension  lines  the  pins  and  cross  arms  should 
be  boiled  in  some  sort  of  oil. 

Insulators  for  medium  voltages  may  be  of  glass  but  for  high 
voltages  porcelain  or  a  combination  of  porcelain  and  glass  is 
best. 

The  wires  should  be  far  apart  (from  18  inches  to  72  inches) 
to  reduce  leakage  and  make  it  difficult  for  a  person  to  throw  a 
stick  across  them  large  enough  to  cause  a  short  circuit,  and  to 
lessen  the  liability  of  birds  causing  shorts. 

The  wires,  other  things  being  equal,  should  be  as  large  as 
possible,  even  as  large  as  one  inch  in  diameter  to  lessen  the 
leakage  of  energy. 

A  stranded  aluminium  wire  of  large  .diameter  is  the  best  con- 
ductor for  the  purpose  if  properly  strung. 

Some  form  of  concrete  pole  or  a  pole  set  in  concrete  makes 
the  cheapest  pole  in  the  long  run. 

The  pole  line  should  be  on  land  controlled  by  the  company, 
and  there  should  be  two  distinct  transmission  lines. 

Modern  tendency  is  toward  concentrating  the  points  of  line 
insulation  and  making  each  pole,  or  tower,  a  more  perfect  in- 
sulating medium.  One  line  lately  constructed  has  spans  of  700 
feet. 


486  HYDROELECTRIC  PLANTS. 

All  voltages  are  practicable  up  to  60,000  or  80,000  volts. 

Three-phase  is  the  cheapest  system  for  long  distance  trans- 
mission. 

The  lower  the  frequency  the  more  efficient  the  transmission. 

Large  wires  (aluminum  wire  is  apt  to  be  large)  have  a  certain 
capacity  which  on  long  lines  is  compensated  for  by  induction 
coils  which  are  cut  out  as  the  load  is  thrown  on. 

If  the  plant  is  well  loaded  there  will  be  little  trouble  from 
induction  or  capacity. 

'  A  large  number  of  lightly  loaded  induction  motors  on  the 
line  reduces  the  power  factor  with  consequent  reduction  of 
carrying  capacity.  A  few  large  synchronous  motors  run  on 
the  same  line  with  the  inductive  load  tend  to  greatly  improve 
the  power  factor. 

EFFICIENCIES. 

There  must  be  some  loss  in  all  transmission  and  transforma- 
tion of  power,  and  it  is  quite  important  to  know  what  per  cent. 
of  the  theoretical  power  will  be  left  for  sale. 

Assuming  that  there  is  no  loss  in  the  water  before  it  gets 
into  position  over  the  wheels  we  will  first  consider  the  turbine. 
In  Fig.  475  is  given  the  efficiency  curves  for  the  more  important 
types  of  turbine.  These  are  the  curves  given  in  the  catalogues 
and  we  may  therefore  assume  that  they  represent  the  best  that 
can  be  expected.  Old  turbines  tested  by  the  author  had  an 
efficiency  of  57  per  cent,  at  full  load. 

For  a  gate  opening  of  from  f  to  full  the  maximum  efficiency 
claimed  is  85  per  cent.  With  decreased  gate  the  efficiency  falls 
off  rapidly  on  some.  The  45-inch  Victor  under  198-foot  head 
has  really  the  best  curve,  though  its  maximum  efficiency  is  only 
78  per  cent.  Few  power  units  are  run  constantly  at  full  gate, 
about  60  per  cent,  being ^nore  nearly  it;  therefore  according  to 
the  turbine  makers  own  statement,  75  per  cent,  is  all  we  can 
expect  at  the  average  load  and  on  low  heads.  On  high  head 
80  per  cent,  should  be  the  average  efficiency. 

"  In  one  pair  of  gears  there  may  be  a  loss  of  10  per  cent." 
(Kent).  If  the  turbine  is  vertical  there  must  be  some  means 
of  transmitting  the  power  to  the  horizontal  shaft  of  the  machine. 
Vertical  generators  are  sometimes  employed,  but  not  usually. 
In  most  cases  gearing  must  be  used.  For  small  turbines  a  crossed 
belt  or  rope  may  be  used  when  the  loss  will  be  about  three  per 
cent. 


POWER     TRANSMISSION. 


487 


In  a  line  shaft  there  will  be  a  loss  of  from  two  to  five  per  cent, 
depending  on  the  alignment  and  character  of  the  oil  and  bearing 
metal.  0.5  to  1  per  cent,  is  lost  at  each  bearing  on  an  average. 

The  next  loss  will  take  place  in  the  generator.  Fig.  476 
shows  the  efficiency  curve  of  a  water  wheel  type,  three-phase 
generator.  This  efficiency  here  shown  does  not  include  the 
excitation,  as  that  is  not  usually  included  in  the  rating  of  the 
generator.  This  loss  will  usually  be  about  two  per  cent.  The 


of  Gate  Open/no 
FIG.  475. — Efficiency  Curves  of  Various  Turbines, 

loss  in  the  two  bearings  of  about  one  per  cent,  is  included  in 
the  curve.  The  power  required  to  drive  the  exciter  is  not 
here  considered  at  all.  The  capacity  of  the  exciter  should  be 
three  to  five  per  cent,  of  the  rated  capacity  of  the  generator. 

The  power  factor  also  has  much  to  do  with  the  efficiency. 
The  size  or  rating  at  which  the  generators  are  sold  is  for  non- 
inductive  load  and  not  an  inductive  load  such  as  transformers, 
motors,  etc., 


488 


HYDROELECTRIC  PLANTS. 


Table  LXXI  gives  the  efficiencies  for  various  sizes  of  core 
type  transformers. 

Transformers  will  carry  a  peak  load  of  100  per  cent. 

The  loss  in  the  transmission  line,  counting  that  at  the  switch- 
board, should  not  be  more  than  six  per  cent  at  full  peak  load, 
as  a  voltage  may  be  selected  which  will  limit  it  to  that  amount. 

Ordinarily  the  hydraulic  power  owner  needs  to  take  his  power 


FIG.  476. — The  efficiency  curve  of  a  generator. 

no  further  than  the  step  down  transformer  at  the  end  of  his 
line,  but  frequently  he  takes  a  contract  to  drive  a  machine  or 
has  to  transform  the  alternating  current  into  constant  current. 

Synchronous  motors  will  not  start  under  full  load  without 
tbe  use  of  friction  clutches,  and  require  several  times  full  load 
current  to  start,  causing  a  heavy  drop  on  the  line. 

Alternating  current  motors  of  the  induction  type  have  a  half 


POWER  TRANSMISSION. 


489 


load  efficiency  of  90  per  cent,  for  large  motors,  75  to  150  h.p., 
and  85  per  cent,  for  the  smaller  sizes.  Synchronous  motors  have 
an  efficiency  slightly  greater  than  that  of  the  induction  type. 

The  losses  from  the  switchboard  to  the  trolley  of  an  electric 
there  is  what  might  be  called  a  back  pressure  set  up  which  re- 
duces the  effective  capacity  of  the  machine.  Thus  with  a  power 
factor  of  .8  such  as  is  common  with  a  load  of  both  motors  and 
lights,  the  capacity  of  the  generator  will  be  only  about  80  per 
cent,  of  the  rated  capacity  though  the  turbine  power  required 
to  drive  the  generator  is  the  rated  capacity  plus  the  usual  50 
per  cent,  overload,  plus  10  per  cent,  for  regulation,  plus  three 
to  five  per  cent,  for  excitation. 


TABLE  LXXI. 
GENERAL  ELECTRIC  TYPE  H  OIL  TRANSFORMERS. 


Ciocker. 


Watts 
capacity. 

Efficiency. 

Weight 
in 
pounds. 

Full  load. 

2  load. 

i  load. 

*  load. 

600 

93.5 

92.9 

91.1 

85.2 

70 

1,500 

95.2 

95. 

94. 

90.3 

125 

2,500 

96. 

95.9 

95.1 

92.1 

195 

4,000 

96.4 

96.4 

95.9 

93.6 

270 

7,500 

96.7 

96.6 

96.2 

94. 

470 

10,000 

96.9 

96.9 

96.4 

94.3 

535 

15,000 

97.1 

97.1 

96.8 

95.1 

850 

25,000 

97.3 

97.4 

97.2 

95.9 

1210 

50,000 

97.7 

97.7 

97.5 

96.1 

1900 

For  all  probable  average  loads  90  per  cent,  is  nearly  the  effi- 
ciency we  may  expect  of  an  alternating  current  generator,  in- 
cluding excitation. 

As  the  generator  voltage  should  not  be  over  11,000  volts, 
transformers  are  used  to  step  up  the  voltage  for  transmission. 
1  In  selecting  the  transformers,  it  is  not  always  best  to  buy 
those  of  highest  efficiency  unless  the  additional  power  lost  in 
the  less  efficient  transformer  would  be  worth  more  than  the 
difference  in  cost. 

In  changing  the  frequency  of  an  alternating  current  by  means 
of  a  synchronous  and  an  induction  motor  from  12  to  14  per 
cent,  is  lost  depending  on  size  and  running  conditions. 


490 


HYDROELECTRIC  PLANTS. 


To  change  an  alternating  current  to  direct  by  means  of  a  syn- 
chronous converter  or  motor  generator,  from  four  per  cent,  to 
eight  per  cent,  is  lost. 

A  loss  of  about  four  per  cent,  is  sustained  in  changing  from 
one  phase  to  another,  being  the  losses  in  the  transformers. 

Fig.  477  gives  the  typical  efficiency  curves  for  the  various 
machines  used  in  hydro-electric  plants. 


AOC 


too 


FIG.  477. — Efficiency  of  various  machines  at  part  load. 

Fig.  478  shows  the  successive  losses  in  a  transmission  system. 
It  starts  with  1000  theoretical  horse  power  in  the  water  and 
takes  it  through  turbine,  gearing,  generator,  step  up  trans- 
formers, substation  and  synchronous  converter,  and  delivers  it 
to  the  trolley.  "  In  the  motors  on  the  car  there  will  be  a  fur- 
ther loss  of  15  per  cent,  due  to  motor  gearing,  wiring,  etc.' 
(Bell). 


I'UU'ER  TRANSMISSION. 


491 


4912 


HYDROELECTRIC  PLANTS. 


POWER  TRANSMISSION.  493 

A  reliable  test  made  on  the  transmission  from  Lauffen  to 
Frankfort  places  the  efficiency  at  about  third  load  as  follows: 

98  h.p.   in     78    h.p.  at     66    h.p  61  h.p.  58  h.p.  to  53.5  h.p. 

the  water,     generator       from  gene-     from  step-  step-down  from-step 

Eff:  =  79.6  rator  up    trans-  trans-  down 

per  cent.        Eff  :  =*  84.6  former.  former.         trans- 

percent.        Eff:  =  92^  Eff :  =  95     former. 

percent.  percent.      Eff:  =  92.2 
per  cent. 

This  gives  an  efficiency  of  about  50  per  cent,  from  the  water 
to  the  customer's  circuit.  The  full  load  efficiency  was  about 
54  per  cent.  The  transmission  109  miles,  voltage  12  to  25,000. 
These  losses  may  seem  excessive  and  yet  they  are  fully  as  good 
as  can  be  attained  in  practice.  If  all  machines  could  be  run  at 
full  load  the  losses  could  be  greatly  reduced,  but  such  would  not 
be  practice,  therefore  we  get  a  51  per  cent,  efficiency  at  the 
end  of  our  line  or  510  h.p.  Ordinarily  this  is  the  amount  of 
power  the  hydraulic  proprietor  would  have  to  sell.  Meters  and 
other  small  losses  would  make  this  about  500  h.p.  or  one-half 
the  theoretical  power  in  the  water  above  the  dam. 

Direct  turbine-generator  connection  would  make  the  loss  from 
turbine  to  generator  80  per  cent.,  cutting  out  the  gearing  loss. 
Crosby  &  Bell  state  that  actual  tests  on  existing  steam  railway 
plants  showed  an  efficiency  from  the  steam,  after  generation, 
to  the  line  of  40  per  cent,  at  Lafayette,  Ind.,  62.8  per  cent.; 
at  Syracuse,  N.  Y.,  and  another  road,  54.6  per  cent.  This  with 
a  line  loss  of  10  per  cent,  and  car  loss  of  25  per  cent.,  gives  an 
efficiency  of  only  40  per  cent,  at  the  car;  and  in  the  above  case 
would  only  deliver  204  of  the  510  h.p.  instead  of  240  h.p.  as 
shown.  Hence,  the  hydraulic  power  plant  has  the  advantage 
after  the  sub-station  is  reached.  Fig.  479  shows  graphically 
the  results  of  tests  on  a  new  transmission  plant. 

EFFICIENCY  OF  OLD  WHEELS. 

In  Fig.  480  is  given  a  set  of  curves  showing  the  efficiency 
of  old  turbines.  These  curves  were  made  from  dynamometer 
tests  on  turbines  in  actual  service.  Curves  1  to  4  inclusive  are 
by  Mr.  Wm.  O.  Webber  and  given  in  a  paper  read  before  the 
American  Society  of  Mechanical  Engineers,  May,  1906.  Curve 
1  was  of  a  39-inch  Hercules  wheel,  in  good  shape  and  of.  compara- 
tively late  design. 

Curve  2  is  of  a  40-inch  Risdon  wheel  cylinder  gate,  which  had 
been  in  use  about  10  years. 


494 


HYDROELECTRIC  PLANTS. 


Curve  3  was  a  very  old  cylinder  gate,  54-inch  Risdon  wheel 
in  good  condition. 

Curve  4,  that  of  a  turbine  of  same  make,  size  and  age  as  3, 
but  had  several  nicks  in  the  buckets. 

Curve  5  is  of  a  New  American  wheel  20  years  old,  tested  by 
Mr.  Wm.  Kramer. 

Curve  6  is  of  a  New  American  wheel  18  years  old,  tested  by 
the  writer. 

These  were  all  vertical  turbines  and  the  curves  all  show  the 


S»o 


/O 


O£        0.3       0.4-       0.3       0.6        0.7       O.G       O3 

FIG.  480. — Efficiency  of  old  water  wheels. 

efficiency  at  end  of  line  shaft  except  the  last,  where  the  dynamo- 
meter was  placed  directly  on  the  turbine  shaft. 

These  curves  are  extremely  valuable  to  the  engineer  as 
showing  the  relative  value  of  old  turbines.  It  will  be  seen 
that  the  half  load  efficiency  in  every  case  but  one  falls  below 
60  per  cent.  Curve  1  may  be  considered  as  being  better  than 
the  average  modern  turbine. 

Mr.  Webber  made  many  tests  of  efficiency  at  different  speeds, 
and  added  emphasis  to  the  fact  that  the  efficiency  rapidly  falls 
off  when  the  turbine  is  run  at  lower  or  higher  speeds  than  that 
for  which  it  is  designed. 


CHAPTER  IX. 
TABLES  AND  FORMULAS. 

In  this  chapter  tables  and  formulas,  which  it  is  thought  will 
be  useful  to  the  engineer,  have  been  compiled.  The  tables 
giving  the  power  and  energy  in  water  under  different  conditions 
were  calculated  by  the  author;  the  rest  of  the  tables  were  com- 
piled from  various  sources,  credit  being  given  in  each  case. 

COMPARISON  OF  HEADS  OF  WATER  IN  FEET  WITH  PRESSURES  IN 
VARIOUS  UNITS  (Kent). 

One  Foot  of  Water  at  39.1°  F.  =62.425  Ib.  per  sq.  ft. 

=     .4335  Ib.  per  sq.  in. 

"      "        "        "         "        =     .0295  atmospheres. 
"      "       "        "         "        =     .8826  in.  of  meicury  at  32°. 
1      "       "         "         "        =     773.3  ft.  of  ah  at  32°. 
One  pound  pe:  sq.  ft.  at  39.1°  F.  =  0.1602  ft.  of  water. 

11     "     "    "          "        =2.307  ft.  of  water, 
atmosphere  at  29.922  in.  of  mercury  =33.9  ft.  of  water. 
"     in.  of  mercury  at  32.1°  F.  =1.133  ft.  of  water. 
"     foot  of  average  sea  water  =1.026  ft.  of  pure  water. 

of  water  at  62°  F.  =62.355  Ib.  per  sq.  ft. 
"      inch  "       "       "  •   .43302  Ib.  per  sq.  in. 

"     pound  of  water  per  sq.  in.  at  62°  F.  =2.3094  ft.  of  water. 

POWER  AND  ENERGY  EXPRESSIONS  AND  THEIR  EQUIVALENTS. 

1.  ampere  at  one  volt. 

0.7373  foot-pounds  per  second. 


One  Watt 


44.238  foot-pounds  per  minute. 
2654.28  foot-pounds  per  hour. 
0.00134  horse-power. 


495 


496 


HYDROELECTRIC  PLANTS. 


One  Kilowatt 


One  Horse  Power       = 


One  Watt-Hour 


[737.3  foot-pounds  per  second. 
44238.  foot-pounds  per  minute. 
1.34  horse-power. 

550  foot-pounds  per  second. 
33000  foot-pounds  per  minute. 
746  watts. 

.746  kilowatts. 


2654.28  foot-pounds. 

1.  ampere-hour  at  one  volt. 

.00134  horse-power  hour. 
0.001  kilowatt-hour. 


1,980,000  foot-pounds. 

One  Horse-Power-Hour  =  -j   746  watts  for  one  hour. 

.746  kilowatt-hours. 

APPLICATION  OF  ENERGY  FORMULAS. 

EXAMPLE  1: — Assume  that  a  given  river  has  a  flow  of  10,000 
cubic  feet  per  minute  which  is  utilized  under  a  head  of  11  feet 
for  10  hours  every  day,  required  the  energy  in  horse-power 
hours  which  is  used  per  day  of  10  hours, 


11x10,000x10 

528 


2.083  horse-power-hours. 


On  the  other  hand,  suppose  that  we  have  a  reservoir  whose 
superficial  area  is  1,500,000  square  feet  and  that  we  can  draw 
down  the  surface  of  this  reservoir  two  feet,  that  is,  we  have 
3,000,000  cubic  feet  of  water  which  can  be  utilized  under  the 
average  head  (allowing  one  foot  for  lost  head)  of  20  feet.  Then, 
substituting  in  the  proper  formula,  in  Table  LXXII,  we  have 
for  100  per  cent,  efficiency, 


20X3,000,000 
31,600 


=  1890  horse-power-hours. 


This  represents  the  total  energy  available  which  if  used  in 
one  hour  would  be  1890  horse-power;  if  used  in  10  hours  would 
be  189  horse-power. 


TABLES  AND  FORMULAS. 


497 


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498 


H  YDROELECTRIC  PLAN TS. 


The  application  of  the  kilowatt-hour  formulas  is  exactly 
similar  to  the  examples  given  above. 

EXAMPLE  2: — Suppose  that  we  have  a  reservoir  whose  super- 
ficial area  is  12  acres  and  that  we  are  able  to  draw  down  the 
surface  two  feet  and  utilize  the  water  under  a  head  of  20  feet. 
What  is  the  number  of  horse-power-hours  per  acre,  assuming 
an  efficiency  of  60  per  cent.  Referring  to  the  proper  formula 
in  Table  LXXII  we  have 

0.825X20X12  =  198  horse-power  hours  per  acre  foot. 

Since  we  are  going  to  use  two  feet,  there  will  be  twice  this 
amount  or  396  horse-power  hours  per  acre.  If  this  energy  is 
utilized  during  10  hours  we  would  have  39.6  horse-power;  if  it 

TABLE  LXXIII. 

THE  HORSE-POWER  IN  WATER,  FLOWING  AT  THE  RATE  OF  ONE  CUBIC  FOOT  PER 

MINUTE  AND  OPERATING  UNDER  VARIOUS  HEADS  AT  AN  EFFICIENCY  OF 

85  PER  CENT. 


Head  h.p.  of 

in   1  cu.  ft. 

feet,  of  water. 

Head.   h.p. 

Head.    h.p. 

Head.    h.p. 

Head. 

'h.p. 

1  .0016088 

36   .057953 

100  .160980 

320  .515136 

640 

1  .030272 

2  .0032196 

38   .061172 

105   .  169029 

330   .531234 

650 

.04637 

3  .0048294 

40   .06439 

110  .177078 

340  .547332 

660 

.062468 

4  .0064392 

42   .067612 

115  .185127 

350   .563430 

670 

.078566 

5  .008049 

44   .070831 

120  .193176 

360  .579528 

680 

.094664 

6  .0096588 

46   .074051 

125  .201225 

370   .595626 

690 

1.110762 

7  .0112686 

48   .07727 

130   .209274 

380  .611724 

700 

1.12686 

8  .0128784 

£0   .08049 

135   .217323 

390   .627822 

710 

1.142958 

9  .0144882 

52   .08371 

140   .225372 

400   .643920 

720 

1.159056 

10  .016089 

54   .086929 

145   .233421 

410   .660018 

730 

1.175154 

11  .0177078 

56   .090149 

150   .241470 

420   .676116 

740 

12  .0193176 

58   .093368 

155   .249519 

430   .692214 

750 

1.20735 

13  .020927 

60   .096588 

160  .257568 

440  .708312 

760 

14  .022537 

62   .099807 

165  .265617 

450   .724410 

780 

15  .024147 

64   .  103027 

170  .273666 

460   .  740508 

790 

16  .025757 

66   .  106247 

175   .281715 

470   .756606 

800 

1.28780 

17  .027366 

68   .  109466 

180  .289764 

480   .772704 

820 

18  .028876 

70   .112686 

185  .297813 

490   .788802 

840 

19  .030586 

72   .115906 

190  .305862 

500   .804900 

860 

20  .032196 

74   .119125 

195  .313911 

510   .820998 

880 

21  .0338058 

76   .122345 

200   .321960 

520   .837096 

900 

1.44882 

22  .0354156 

78   .125564 

210   .338058 

530   .853194 

920 

23  .037025 

80   .128784 

220   .354156 

540   .869292 

940 

24  .038635 

82   .132004 

230   .370254 

550   .885690 

960 

25  .040245 

84   .135223 

240   .386352 

560   .901488 

980 

26  .041855 

86   .  138443 

250   .402450 

570   .917586 

1000 

1.60980 

27  .043464 

88   .141662 

260   .418548 

580   .933684 

28  .045074 

90   .144882 

270   .434646 

590   .949782 

29  .046684 

92   .148102 

280   .450744 

600   .965880 

30  .048294 

94   .151321 

290   .466842 

610   .981978 

32  .051514 

96   .154508 

300   .482940 

620   .998076 

34  .054733 

98   .157760 

310   .499038 

630  1  .014174 

TABLES  AND  FORMULAS. 


499 


TABLE  LXXIV. 

THEORETICAL  KILOWATTS  IN  WATER  FLOWING  AT  THE  RATE  OF  ONE  CUBIC  FOOT 
PER  MINUTE  AND  OPERATING  UNDER  VARIOUS  HEADS. 


Head. 

kw. 

Head. 

kw. 

Head. 

kw. 

Head. 

kw. 

Head. 

kw. 

4 

.00565 

100 

.1413 

330 

.4663 

560 

.7913 

790 

.116 

5 

.00706 

105 

.1483 

335 

.4734 

565 

.7984 

795 

.123 

6 

.00848 

110 

.1554 

340 

.4804 

570 

.8054 

800 

.130 

7 

.00989 

115 

.1625 

345 

.4875 

575 

.8125 

805 

.137 

8 

.01130 

120 

.1659 

350 

.4946 

580 

.8195 

810 

.145 

9 

.01271 

125 

.1766 

355 

.5016 

585 

.8266 

815 

.1516 

10 

.01413 

130 

.1837 

360 

.5087 

590 

.8337 

820 

.159 

11 

.01554 

135 

.1907 

365 

.5  57 

595 

.8407 

825 

.166 

12 

.01695 

140 

.1978 

370 

.5288 

600 

.8478 

830 

.173 

13 

.01837 

145 

.2049 

375 

.5299 

605 

.8548 

835 

.181 

14 

.01978 

150 

.21195 

380 

.5369 

610 

.8619 

840 

.188 

15 

.02159 

155 

.2190 

385 

.5440 

615 

.8690 

845 

.195 

16 

.0226 

160 

.2260 

390 

.5510 

620 

.8760 

850 

.201 

17 

.02402 

165 

.2331 

395 

.5580 

625 

.8830 

855 

.208 

18 

.0254 

170 

.2402 

400 

.5650 

630 

.8902 

860 

.215 

19 

.02684 

175 

.2477 

405 

.5720 

635 

.8970 

865 

.2222 

20 

.02826 

180 

.2543 

410 

.5790 

640 

.9040 

870 

1.229 

21 

.02967 

185 

.2614 

415 

.5864 

645 

.9112  • 

875 

1.2364 

22 

.031086 

190 

.2684 

420 

.5935 

650 

.9184 

880 

1.2434 

23 

.03259 

195 

.2755 

425 

.6005 

655 

.9255 

885 

1.2505 

24 

.03391 

200 

.2826 

430 

.6076 

660 

.9326 

890 

1.2576 

25 

.0353 

205 

.2895 

435 

.61466 

665 

.9396 

895 

1.2646 

26 

.0367 

210 

.2966 

440 

.62173 

670 

.9467 

900 

1.2717 

27 

.03815 

215 

.3037 

445 

.6288 

675 

.9538 

905 

1.2787 

28 

.03956 

220 

.3107 

450 

.6359 

680 

.9608 

910 

1.2858 

29 

.04097 

225 

.3179 

455 

.6429 

685 

.9674 

915 

1  .  2929 

30 

.0424 

230 

.3245 

460 

.6500 

690 

.9750 

920 

1.2300 

32 

.0452 

235 

.3320 

465 

.6570 

695 

.9820 

925 

1.307 

34 

.04804 

240 

.3390 

470 

.6640 

700 

.9890 

930 

1.314 

36 

.05086 

245 

.3462 

475 

.6712 

705 

.9960 

935 

.3211 

38 

.0537 

250 

.3530 

480 

.6782 

710 

.003 

940 

.3282 

40 

.0565 

255 

.3603 

485 

.6853 

715 

.0103 

945 

.3353 

42 

.05934 

260 

.3674 

490 

.6924 

720 

.0173 

950 

.3423 

44 

.06217 

265 

.3744 

495 

.6994 

725 

.0244 

955 

.3494 

46 

.065 

270 

.3815 

500 

.7065 

730 

.0315 

960 

.3565 

48 

.0677 

275 

.3886 

505 

.71360 

735 

.1390 

965 

.3635 

50 

.07065 

280 

.3956 

510 

.72060 

740 

.0426 

970 

.37 

55 

.0777 

285 

.4027 

515 

.7277 

745 

.053 

975 

.377 

60 

.08478 

290 

.4098 

520 

.7348 

750 

.0600 

980 

.384 

65 

.09184 

295 

.4168 

525 

.7418 

755 

.067 

985 

.391 

70 

.0989 

300 

.4239 

530 

.7489 

760 

.074 

990 

.399 

75 

.1059 

305 

.4310 

535 

.7560 

765 

.081 

995 

.406 

80 

.11304 

310 

.4380 

540 

.7630 

770 

.088 

1000 

.413 

85 

.1211 

315 

.4451 

545 

.7700 

775 

.095 

90 

.12717 

320 

.4522 

550 

.7770 

780 

.103 

95 

.1342 

325 

.4592 

555 

.7842 

•785 

.110 

500 


HYDROELECTRIC  PLANTS. 


is  utilized  in  one  hour  we  would  have  396  horse-power.  If 
this  energy  can  be  sold  for  lighting  purpose  and  brings  for  ex- 
ample seven  cents  per  horse-power-hour  each  acre-foot  of  reser- 

TABLE  LXXV. 

THE  THEORETICAL  KILOWATT-HOURS  AND  HORSE-POWER-HOURS  PER  ACRE-FOOT 
OF  STORAGE  AREA  FOR  DIFFERENT  HEADS. 


Head 
ft. 

En 
h.p.-hr. 

ergy. 
kw.-hr. 

Head 

ft. 

En 
h.p.-hr. 

ergy. 
kw.-hr. 

Head 

ft. 

En 
h.p.-hr. 

ergy. 
kw.-hr.  . 

4 

5.5 

4.103 

150 

206  .  25 

153.863 

580 

797.50 

594.93 

5 

6.88 

5.129 

160 

220. 

164.120 

590 

811.25 

605  .  19 

6 

8.25 

6.155 

170 

233  .  75 

174.378 

600 

825.00 

615.45 

7 

9.62 

7.180 

180 

247.50 

184.635 

610 

838.75 

625.71 

8 

11.00 

8.206 

190 

261.25 

194.893 

620 

852.50 

635.96 

9 

12.37 

9.232 

200 

275.00 

205.150 

630 

866.25 

646.22 

10 

13.75 

10.258 

210 

288.75 

215.408 

640 

880.00 

656.48 

11 

15.12 

11.283 

220 

302.50 

225.666 

650 

893.75 

666.74 

12 

16.50 

12.309 

230 

316.25 

235.923 

660 

907.50 

676.99 

13 

17.90 

13.335 

240 

330.00 

246.180 

670 

921.25 

687.25 

14 

19.24 

14.361 

250 

343.75 

256.438 

680 

935.00 

697.51 

15 

20.62 

15.386 

260 

357.50 

266  .  69 

690 

948.75 

707  .  77 

16 

22.00 

16.412 

270 

371.25 

276.95 

700 

962.50 

717.92 

17 

23.37 

17.438 

280 

385.00 

287.21 

710 

976.25 

728.18 

18 

24.75 

18.464 

290 

398.75 

297.47 

720 

990.00 

738.44 

19 

26.13 

19.489 

300 

412.50 

307.72 

730 

1003.75 

748.70 

20 

27.50 

20.515 

310 

426  .  25 

317.98 

740 

1017.50 

758.95 

21 

28.87 

21.54 

320 

440.00 

328.24 

750 

1031.25 

769.21 

22 

30.25 

22.566 

330 

453.75 

338.50 

760 

1045.00 

779  .  47 

23 

31.62 

23.592 

340 

467.50 

348.75 

770 

1058.75 

789.72 

24 

33.00 

24.618 

350 

481.25 

359.01 

780 

1072.50 

799.98 

25 

34.37 

25.644 

360 

495.00 

369.27 

790 

1086.25 

810.24 

26 

35.75 

26.670 

370 

508.75 

379.53 

800 

1100.00 

820.50 

27 

37.12 

27.699 

380 

522.50 

389.78 

810 

1113.75 

830.76 

28 

38.49 

28.72 

390 

536.25 

400.04 

820 

1127.50 

841.01 

30 

41.25 

30.772 

400 

550.00 

410.30 

830 

1141.25 

851.27 

32 

44.00 

32.824 

410 

563.75 

420.56 

840 

1155.00 

861.53 

35 

48.12 

35.901 

420 

577.50 

430.81 

850 

1168.75 

871.79 

40 

55.00 

41.030 

430 

591.25 

441.07 

860 

1182.50 

882.04 

45 

61.87 

46  .  159 

440 

605.00 

451  .33 

870 

1196.25 

892.30 

50 

68.75 

51.288 

450 

618.75 

461.59 

880 

1210.00 

902.56 

55 

75.62 

56.416 

460 

632.50 

471  .84 

890 

1223.75 

912.82 

60 

82.50 

61.538 

470 

646.25 

482  .  10 

900 

1237.50 

923.07 

65 

89.37 

66.667 

480 

660.00 

492.36 

910 

1251.25 

933  .  43 

70 

96.25 

71  .803 

490 

673.75 

502.62 

920 

1265.00 

943.69 

75 

103.12 

76.931 

500 

687.50 

512.87 

930 

1278.75 

953.95 

80 

110.00 

82.060 

510 

701.25 

523.13 

940 

1292.50 

964.20 

90 

123.75 

92.318 

520 

715.00 

533.39 

950 

1306.25 

974  .  46 

100 

137.50 

102.575 

530 

728.75 

543.65 

960 

1320.00 

984.72 

110 

151.25 

112.833 

540 

742.50 

553.90 

970 

1333.75 

994.98 

120 

165.00 

123.092 

550 

756.25 

564.16 

980 

1347.50 

1005  .  23 

130 

178.80 

133.348 

560 

770.00 

574  .  42 

990 

1361.25 

1015.49 

140 

192.50 

143.605 

570 

783.75 

584.68 

1000 

1375.00 

1025.75 

voir  area  will  bring  $13.86  each  time  it  is  passed  through  the 
turbines. 


TABLES  AND  FORMULAS. 


501 


COMPARISON  OF  THE  VALUE  OF  POWER  WHEN  EXPRESSED  IN 

HORSE-POWER  PER  YEAR   OR    KlLOWATT  PER  YEAR. 

Since  the  power  of  a  stream  is  usually  sold  in  terms  of  kilowatt- 
hours,  it  is  often  necessary  to  transfer  horse-power-hours  to 
kilowatt-hours;  for  example,  if  one  horse-power  is  used  every 
hour  of  the  year  (8,760)  there  would  be  used  8,760  horse-power- 
hours  per  year.  This  expressed  in  kilowatt-hours  would  equal 
6,535  kilowatt-hours.  If  one  horse-power  is  used  10  hours  a 
day  for  a  year  (3,598  hours)  the  total  energy  would  be  3,598 
horse-power-hours  which  is  2,684  kilowatt-hours. 

Table  LXXVI  gives  the  value  for  different  periods  of  use  of 
one  horse-power  when  sold  at  one  cent  per  kilowatt-hour  and 
vice  versa. 

For  any  other  price,  multiply  the  values  given  in  Table  LXXVI 
by  the  price  in  cents. 

TABLE  LXXVI. 
COST  OF  POWER  FOR  DIFFERENT  PERIODS  OF  USE. 


Hours  one  kw. 
is  used  per  day. 

Cost  per  kw. 
year  at  Ic. 
kw. 
(1) 

and  h.p.  per 
per  kw.-hr. 
h.p. 
(2) 

Cost  per  h.p. 
year  at  Ic.  ] 
h.p. 
(3) 

and  kw.  per 
aer  h  p.-hr. 
kw. 
(4) 

Hours  used 
per  year. 

24 

$87.60 

$65.70 

$87.60 

$109.50 

8.760 

10 

31.30 

23.47 

31.30 

34.12 

3,130 

8 

29.20 

21.09 

29.20 

36.50 

2,920 

8* 

25.04 

18.78 

25.04 

31.30 

2,504 

6* 

21.90 

16.42 

21.90 

27.37 

2,190 

*  Including  Sundays. 

APPLICATION  OF  TABLE  LXXVI. 

If  horse-power  is  worth  $50.00  for  a  year  of  3,130  hours  and, 
it  is  desired  to  know  how  much  this  will  be  per  kilowatt-hour 
divide  $50.00  by  the  price  per  horse-power  in  column  2.  Thus, 

$50.00 


23.47 


=  2.13  cents  per  kilowatt-hour. 


Again  suppose  the  price  to  be  $25.00  per  kilowatt  for  a  year 
of  2,920  hours  the  price  per  kilowatt-hour  being  desired,  then 
$25.00  divided  by  the  cost  of  one  kilowatt  at  one  cent  per  hour, 
that  is,  $29.20  gives  0.856  cents  per  kilowatt-hour. 


INDEX. 


ABUTMENTS,  amount  of  material  in, 
278. 

design  of,  278. 

reinforced  concrete,  280. 

solid  concrete,  279. 
Air  engine.     See  Motors. 
Air  flow  in  pipes,  30. 

heating  of,  379. 

moisting  of,  378. 

motors.     See  Motors. 

valves  in  penstocks,  352. 
Alignment  of  machinery,  43 1 . 
Aluminum  for  bus-bars,  400. 

line,  wire,  475. 

tensile  strength,  475. 
Ammeter.     See  Instruments. 
Anchor  ice,  299. 

protecion  against,  300. 
Anderson  Dam,  profile  of,  239. 
Angle  of  repose,  rule  for,  189. 
Arches,  concrete  forms  for,  95. 
Architecture    for    power    house, 

330. 
Austin  Dam,  profile  of,  239. 

BACK  water  conditions,  340. 

Batch  mixer,  93. 

Beams,  concrete-steel,  120. 

design  of,  126,  128. 

general  formulas,  114. 

properties  of,  123. 
Beardsley  current  meter,  36. 
Bearing  strength  of  various  mate- 
rials, 124. 

Bearings.     See     Power    Transmis- 
sion. 

alignment  of,  431. 

installation  of,  432. 
Belle  Fourche  dam,  270. 
Belting.    See  Power  transmission. 
Blasting  machine,  cost  of,  159. 
Boilers,     See  Power  plants. 
Boosters,  424. 

Bouzey  Dam,  profile  of,  239. 
Brick  wall,  cost  of,  112. 
Bridges,  design  of,  164. 
Bridge-trees,  445. 

cost  of,  446. 
Building  blocks,  111. 

cost  of,  112. 

moulds  for,  111. 


Buoyancy,  2. 

Burnt  clay,  88. 

Bus-bars,  contact  surface,  401. 

design  of,  400,  401. 

high-tension,  402. 

skin  effect,  402. 

CABLES,  deflection  of,  162. 
Cableways,  159. 
cheap,  160. 

for  dam  construction,  160. 
Caisson,   cost   of  excavation  from, 

179. 

cost  of  sinking,  179. 
design  of,  175. 
Canals, 

banks,  shape  of,  31. 
excavation,  cost,  191. 
flow  in,  31. 
lining  of,  189. 
cost  of,  190. 
effect  on  flow,  190. 
location  of,  187. 
masonry,  192. 
reinforced  concrete,  192. 
velocities,  for  various  soils,  32. 
Cement,  69. 

chemical  analysis,  71. 
consistency  of,  74. 
fineness  of,  73-83. 
kinds  of,  70 
purity,  84. 
sampling  of,  70. 
soundness,  83. 
specific  gravity,  72. 
testing,  70. 

beam  test,  85. 
constancy  of  volume,  81. 
mixing,  78. 
molding,  79. 
molds,  78. 
simple,  82. 
storage  of  pieces,  80. 
tensile  strength,  80. 
time  of  setting,  76-83. 
uses  of,  85. 
weight,  85. 

Center  of  gravity,  method  of  find- 
ing, 256. 

Channeling  machine,   155. 
cost  of,  155. 


503 


504 


INDEX. 


Chimneys,  design  of,  386. 

foundations,  386. 

guying  of,  386. 
Churn  drilling,  149. 
Circuit-breaker,  407. 

high  tension,  408. 

installment,  408. 
Clay,  shrinkage  of,  268. 
Coefficient  of  roughness,  values  of, 

22. 
Coffer  dams,  169. 

cost  of,  174. 

horse  type,  171. 
cost  of,  173. 

ordinary  type,  174. 

sand  bag  type,  169. 

sacks  necessary  to  build,  171. 

truss  bridge  type,  173. 
Columbus  Dam,  profile  of,  239. 
Columns,  design  of,  122,  129. 

general  formulas,   114. 
Compensator,  405,  406. 
Compressed  air,     See  Air. 
Concrete,  69. 

abutments,  cost  of,  110. 

aggregates,    for    various    pur- 
poses,  87. 

amount  of  water  used  in  mix- 
ing, 87. 

bus  hammering,   112 

coloring  of,  112. 

crushing  strength,  122. 

expansion  of,  100. 

exposed  to  sun,  100. 

facing  boards,  97. 

forms,  building  of,  94. 

freezing  weather,  91-100. 

hand  mixed,  cost  of,  89. 

hand  mixing  methods,  90. 

laid  under  water,  98. 

laying  of,  99. 

machine  mixing,  methods,  92. 

piles,    See  Piles. 

rock  work,  96. 

shrinkage  of,  102. 

strength,    effect,    of    age    and 
frost,    101. 

strength  of,   for  various  ages, 
91. 

surfacing  of,  96. 

tensile  strength,  100. 

weight  of,  86. 

work,  cost  of,  88. 
Concrete-steel,  102. 

beams,  design  of,  120. 

hollow  construction,  104. 
forms  for,  104. 

power  house,  cost  of,  110. 
Copper  bus-bars,  400. 

line,  wire,  475. 


Cornell    experiments    on    flow-over 

dams,    14. 
Cost  of:  brick  penstocks,  208. 

walls,  112. 
bridge-trees,  446. 
building  blocks,  112. 
canal  lining,  190. 
channeling  machine,  155. 
coffer  dam,  174. 
compressed     air    transmission 

system,   380. 

concrete  abutments,  110. 
concrete  work,  89. 
concrete-steel  chimney,  386. 
penstocks,  109,  208. 
poles,  467. 
power  houses,  110. 
construction     equipment     for 

earth  dams,   269. 
diamond  drill,  151. 
drill  tripod,  152. 
drills,  152,  154. 
earth  dams,  270. 
Edson  pile  sinking  outfit,  142. 
electric     power     transmission, 

380. 

energy,  501. 

excavation  from  caissons,  179. 
explosives,  159. 
gas  engines,  393. 
gas  producers,  393. 
hand  drilling,  150. 
high  speed  engines,  388. 
horse  coffer  dam,   173. 
hose  pipe,  153. 
hydraulic  fill  plant,  274. 
hydro-compressor  installation, 

379. 

insulator  pins, 471. 
insulatore,  473,  474. 
laying  mats,  223. 
locomotive  boiler,  382. 
maintenance    of  steam    power 

plant,   427. 
marble,  399. 
mining  column,  153. 
operation  steam  boiler,  382. 
pile  drivers,  140. 
pile  driving,  140. 
puddle,  268. 
reinforced  concrete  penstocks, 

109,  208. 
round  piles,  141. 
sand  cement,  88. 
sawing     outfit     for     penstock 

staves,   204. 
setting  poles,  464. 
sheet  piling,  140. 
sinking    caissons    in    different 

soils,    179. 


INDEX. 


505 


Cost  of:  slow  speed  engines,  388. 
steam  power  plant,  51,  427. 
steel  stacks, -386. 
storage     batteries     operation, 

428. 

surveys,  61. 
switchboards,  399. 
transformers,  417. 
turbine  harness,  446. 
various  types  of  dams,  274-278. 
water  tube  boiler,  382. 
Couplings.  See  Power  transmission. 
Cross  arms,     See  Power  transmis- 
sion. 

Croton  Dam,  profile,  258. 
Current  density  in  bus-bars,  400. 
meters,  35. 

direct  reading  type,  36. 
revolving  type,  35. 

DAMS,  effect  on  back  water,  340. 
agents  of  destruction,    graph- 
ically represented,  250. 
amounts  of  material  required 

for  various  types,  274. 
apron,  design  of,  227. 
bow,  237. 
coffer,     See  Coffer, 
concrete,  deposition  of,  264. 
concrete-steel,  233. 
cost  of  various  types,  274. 
design  of,  210. 
down-stream  push,  241. 
earth,  265. 

building  of,  268. 

construction     equipment, 
269. 

construction     equipment, 
cost  of,   269. 

cost,  270. 

drainage  of,  269. 

hydraulic  fills,  cost  of  plant 
274. 

hydraulic  fills,  waters  re- 
quired for,  274. 

materials  for,  267. 

most  famous,  273. 

profiles  for,  273. 

puddle  mixture,  267. 

site,  266. 

weir  in,  271. 

factors  in,  design  of,  238. 
flash  boards.  See  Flash  boards. 

design  of,  281. 
floatation  of,  247. 
flow  over,  12. 
frame  type,  224. 
friction  on  bed  of  stream,  241. 
gravity,  choice  of  slope,  218. 

concrete-steel  design,  227. 


Dams,  gravity,  concrete-steel,   rock 

bottom,  229,  230. 
concrete-steel,  segmental, 

231. 

frame  type,  design  of,  224. 
•  reinforced  concrete,  234. 
segmental,  231. 
steel,  227. 
theory  of,  216. 
timber,  rock  bottom,  225. 
timber,  soft  bottom,  226. 
ice  expansion,  247. 
masonry,  238. 

apron,  design  of,  254. 
center  of  gravity,  256. 
crushing  stresses,  255. 
design  of,  251. 
design,  practical  example, 

259. 

safety  of  any  section,  253. 
standard  profile,  258. 
mats.     See  Mats, 
movable,   235,   285-289. 
nappe,  form  of,  17. 
over  pour,  form  of,  15. 
pressures  on,  217. 
sand  bottom,  218. 
seepage  under,  248. 
standard  section,  262. 
steel,  232. 
Tainton  gate,  350. 
timber,  choice  of  material,  219. 
vacuums,  241. 

action  of,  242. 
which  have  failed,  239. 
wing,  236. 
Depreciation    and    maintenance 

charges,   66. 

Diamond  drill,  cost  of,  151. 
Distribution  a.c.,  394. 

polyphase,  396. 
single-phase,  394. 
three-wire,  396. 
systems,  394. 

two-phase,  vs.  three-phase 

397. 

continuous  current,  393. 
parallel,  394. 
series  system,  393. 
wiring  methods,  394. 
systems,  393. 
Draft  head,  343. 
Draft  tubes,  342. 

conical  forms,  343. 
deflector  for,  313. 
diameters  for  different 

heads,   343. 
installation  of,  343. 
Drill  hose  pipe,  cost  of,  153 
Drill,  mining  column,  cost  of,  153. 


506 


INDEX. 


Drilling,  149. 

by  hand,  cost  of,   150. 

by  machine,  151. 

machine,  attendance  required, 
154. 

size  of  air  pipe,  193. 
Drills,     blacksmiths     required     for 
sharpening,    155. 

cost  of,  152,  154. 

steam  required  by,  152. 

tripod,  cost  of,  152. 
Drum  hoist,  design,  134. 
Dynamite,  cost  of,  159. 

handling  of,  155. 

preparation  of,  156. 
Dynamometer,     absorption.        See 
Prony  brake. 

EARTH  dams,  see  dams. 
Edson  pile  sinking  outfit,  142. 
Efficiency    as    affected    by    power 
factor,  487. 

of  various  machines,  64,  487. 
Ejector  gates.  310. 
Electric  fuses,  cost  of.  159. 
Electric    generators.       See    Gener- 
ators. 
Electric  transmission.     See   Power 

transmission. 
Embankments,  185. 

design,  187. 

materials  suitable  for,  186. 

preparation  of  ground  for,  185. 

puddle  wall,  design  of,   186. 

riprap  for,  187. 

slope,  height  of,  186. 
Energy  cost,  501. 

formulas,  497. 

application  of,  497. 
Engine  foundations,  303. 

gas.    See  Power  plants,  gas. 

steam.  See  Power  plants. steam. 
Excavation,  cost  of,  179. 
Exciters,     See  Powei -house. 
Expander,  205. 
Explosions,  boilers,  383. 
Explosives,  155. 

FACTORS  of  safety,  125. 

Feed  water.    See  Power  plants. 

Flash  boards,  281. 

adjustable,  285-289. 

design  of  posts,  283. 

forms  of,  281. 

short  dam,  283. 

vacuum  under,  283. 
Floatation,  2. 
Floats,  35. 

Flood,  maximum  determination  of, 
43. 


Flood  periods,  determination  of,  43. 
Flow,  curves  showing,  50. 

effect  of  ice  on,  32. 

measurement  of,  10. 

integrating  method,  38. 
single  point  method,  36. 
six    tenths     single     point 
method,  37. 

of  air,     See  Air. 

of  water.    See  Water. 
Flowage  height,  58. 
Flume,  303. 

area  of,  345. 

built  in  gravity  dam,  303. 

discharge  velocity,  344. 

effect  of  depth  of  tail  water, 
345. 

floor  of,  345. 

interior  velocity,  344. 

tail  race,  345. 

timber,  305. 
Fly-wheels,  energy  stored  in,  363. 

use  of,  358. 

Forms  for  concrete  work,  94 
Formulas  and  tables,  495. 
Foundations,  301. 

design  of,  122. 

engine,  303. 

materials,  strength  of,  302. 
Frequency  changers,  429. 

efficiency,  430. 
Friction.     See  Power  transmission. 

clutches.    See  Power  transmis- 
sion. 

coefficient,  453,  458. 

head,  5. 

head  in  rivers,  60. 
Fuses,  408,  409. 

GAS  engines.    See  Power  plants. 
Gate  hoists,  294. 
Gauge  boxes,  size  of,  90. 
Gauges  on  turbine  settings,  343. 
Gears.     See  Power  transmission. 
Generators,  393, 

efficiency,  487. 

rating  of,  398. 

selection  of,  397. 

voltage,  489. 

work,  394. 

Giant  used  for  hydraulic  fills,  273. 
Governing   of   high   speed   turbine 

insulations,   365. 

Government  reports,  value  of,  40. 
Governors,   actuated  from  switch- 
board,  359. 

cheap,  353. 

hydraulic,  358. 

mechanical,  359. 

operation  of,  359. 


INDEX. 


507 


Governors,  turbine,  353. 

requirements  for,  361. 

types  on  market,  358. 

Woodward,  types  C  and  D.354. 
Gravity  mixer,  93. 
Grounded  guard  wire,  485. 
Guard  wire,  grounded,  485. 
Gumbo,  88. 

HABRA  Dam,  profile  of,  239. 
Hand  drilling,  149. 
Hard  pan,  211. 
Harness  for  turbines,  445. 
Head  gates,  289. 
cost  of,  293. 
design  of,  294. 
force  to  start,  295. 
high  heads,  294. 
hoists,  296. 

hydraulically  operated,  297. 
large  work,  "290. 
medium  heads,  293. 
most  common  form,  289. 
soft  bottom,  289. 
velocity  through,  290. 
Head  racks,  298. 
anchor  ice,  299. 
boom,  299. 
cheapest  form,  298. 
cost  of,  299. 
net  area,  298. 
velocity  permissible   during 

floods,   342. 
weight  of,  299. 
Heads  of  water,  conversion  table, 

495. 
High    head    turbine,     installations 

governing  of,   365. 
Hoists  for  gates,  294. 
Hook  gauge,  368. 
Horse-power  in   water   at    various 

heads,   498. 
stored  in  water,  500. 
Hydraulic  construction,  137. 
fills,  273. 
gradient,  5. 
power  formulas,  497. 
radius  for  different  size  pipe, 

29. 
ram,  183. 

calculation  of,  data,  184. 
capacity    of    the    several 

sizes,    185. 

Hydro-compressors,  371,  372. 
Ainsworth,  374. 
air  head,  377. 

mixing  pipe,  377. 
reservoir,  377. 

compressor  pipe,  not  in  well, 
376. 


Hydro-compressors,   data,  375. 

design  of,  376. 

efficiency,  374,  376. 

head  gates,  377. 

inlet  pipes,  377. 

installation  cost,  379. 

Magog,  P.  Q.,  374. 

pressure,  selection  of,  376. 
variation,  374. 

velocity  in,  376. 

Victoria  mines,  Michigan,  374. 
Hydrodynamics,  2. 
Hydrostatics,  1. 

ICE,  blasting  of,  158. 
effect  on  flow,  32. 
evils,  55. 

expansion  of,  247. 
expansive  power  of,  248. 
Imperial  gallons,  1 . 
Impulse  pressure,  8. 
Inductive  reactance  in  transmission 

lines,  481. 
Instruments. 

ammeter,  recording,  407. 

West  on,  407. 

ampere-hour  meters,  413. 
two  rate  meters,  413. 
voltmeter,  a.c.,  404. 
d.c.,  404. 
electrostatic,  405. 
watt-hour  meters,  409. 
accuracy  of,  411. 
connections,  411. 
induction,  411. 
Thomson,  410. 
wattmeters,  409. 

Insulator  pins.     See  Power  trans- 
mission. 
Internal  combustion  engine.      See 

Power  plants. 
Iron  piling.    See  Piling. 

JEROME  Park  reservoir,  269. 
Jovite,  158. 

cost  of,  159. 
Jump  drilling,  149. 

KAHN  bar,  reinforcement,  104. 
Keys.    See  Power  transmission. 
Kilowatt-hours  in  water  in  stored 

water,  500. 
Kilowatts  in  water  at  various  heads 

499. 
Kutter's  formula,  values  of  C,  26. 

LEFFEL  turbine,  333. 
Lightning. 

arresters,  413. 
a.c.,  413. 


508 


INDEX. 


Lightning,  arresters,  connections  of, 
413-415. 

Garton,  413. 

General  Electric,  413. 

grounding  of,  484. 

low-equivalent,  415. 

West  high  ouse,  413. 
protection,  407,  484. 
Lower  Tallasee  Dam,  profile  of,  239. 
Lubricants,  458. 

MACHINES,  alignment  of,  431. 
Maintennace    and    depreciation 

charges,   66. 

Masonry,  bearing  strength,  124. 
Materials,  68. 
Mats,  Beardsley, 

concrete  steel,  cost  of,  214. 
cost  of  laying,  223. 
extension,  215. 

cheapest  kind,  216. 
for  abutments  and  walls,  302. 
length  of,  222. 
rock  bottom,  213. 
sand  bottom,  212. 
soft  bottom,  210. 
Measurements,  engineer's,  62. 
Mershon  diagram,  480. 
Metals,  69. 
Meters,   See  instruments. 

Venturi  meter,  18. 
Instruments. 

Mill  Creek  penstock  system,  calcu- 
lation of,  53. 
power  plant,  52. 
Miner's  inch,  1. 
Mining  column,  cost  of,  153. 
Moment,  definition  of,  113. 
inertia,  definition  of,  113. 

in  built-up  sections,  126. 
resistance,  definitions  of,  113. 
Motors. 

air,  378,  380. 
air  consumption  of,  380. 
water  required  to  saturate  air, 

379. 
electric,  single-phase,  395. 

induction,     as    frequency 
changers,   430. 

efficiency,  489. 
single-phase     advantages, 

395. 
synchronous,    efficiency, 

489. 

starting  current,  488. 
Motor-generators,  429. 
efficiency,  490. 

NAPPES,  form  of,  17. 
Needle  nozzle,  365,  366. 


Neutral  line,  definition  of,  113. 
Niagara  Falls  power  house,  328. 

ORIFICES.     See  Water. 

PELTON  wheel,  347. 

regulation  of,  348,  349. 
needle  nozzle,  365. 
Penstocks,    abnormal    pressures  in, 
349. 

brick,  cost  of,  208. 

bridge,  168. 

circular,  23,  203. 

concrete-steel,  105. 
cost  of,  109. 

data,  200. 

definition  of,  199. 

expander,  205. 

flow  in,  20,  22. 

Kutter's,  formula,  25. 

gravity  type,  53. 

hoops  for,  206. 

joints,  method  of  making,  203. 

means  of  shutting  off  water, 
361. 

reinforced    concrete,    cost    of, 
208. 

staves,  material  for,  203. 

safety  valves  in,  352. 

joint  sawing  outfit,  204. 

steel,  208. 

joints,  210. 

stresses  in,  207. 

timber,  design  of,  200. 

on  trestle,  202. 

vibration    in,     prevention    of, 

349 
Pile  drivers,  139. 

cost  of,  140. 

methods,  141. 
Pile  screw  outfit,   147. 
Piles,  bearing  power  of,  148. 

concrete,  143. 

hammers  used  with,  145. 

cost  of  driving,  140. 

iron  points,   139. 

jet  driving,  142. 

jet  piles,  cost  of,  142. 

in  quicksand,  140. 

sand,  148. 
Piling,  137. 

iron,  146. 

sheet,  driving  of,   138. 

steel,  145. 

Pins,  insulator.     See  Power  trans- 
mission. 
Pipes,  abnormal  pressures  in,  349. 

capacity,  diagram,  25. 

capacity,  table,  21,  24. 

flow  in,  20. 


INDEX.  509 

Plant   maintenance   and    deprecia-      Powerhouse,   steam,  boilers,  water 
tion  charges,  66.  tube,      space      oc- 

Plumb  lines,   431.  cupied  by,  383. 

Pole  lines.   See  Power  transmission.  coal  required,  381. 

Poles.    See  Power  transmission.  cost  of,  427. 

Pondage,  relation  to  value  of  power,  cost  of  maintenance,  427. 

45.  engines,  388. 

Portland  cement,  70.  comparison  of,  388. 

Power  in  a.c.  circuits,  410.  cost,  388. 

Power  and  energy  expressions,  495.  cut-off,  389. 

Power  factor,    effect   on    rating  of  design,  389. 

generator,   398.  efficiency,  388. 

Power  house,  al  gnment  of  machin-  foundation,  432,  433. 

ery,   431.  overload  capacity,390 

architecture,  330.  power  formula,  388. 

auxiliary,  380.  feed  water  heating,  385. 

Chicago  drainage     canal,   323-  fuels,  comparison  of,  382. 

326.  smoke  stacks,  386. 

concrete-steel,  307.  cost  of,  386. 

construction,  301.  turbines,    overload    capa- 

cost  of,  307.  city,   391. 

with  ejector  gates,  310.  storage  batteries.    See  Storage 
equipment,  331.  batteries, 

exciters,  398.  structure,  303. 

capacity,  398.  switchboards,  398. 
flume,  303.  building  of,  399. 

foreign  types,  321.  bus  work,  400. 

foundations,  301.  cost  of,  399. 

gas  capacity,  391.  frame,  design  of,  399. 

gas  consumption,  393.  instruments.     See  Instru- 

engines,  390.  ments. 

efficiency,  393.  •  materials,  399. 

heat  balance,  390.  remote  control,  402. 

investment,  391.  spacing   of   bus-bars   and 

mixture  used,  392.  switches,   401. 

producers,  cost  of,  393.  switches,  See  Switches, 

generators,  electric.     See  gen-  timber  and  concrete,  307. 

erators.  Power,  measurement  of,  410. 

selection  of,  397.  per  cubic  foot  of  air  at  different 
high  heads,  325,  326.  pressures,  31. 

lightning  protection.  See  Light-  single-phase  circuit,  410. 

ning.  three-phase  circuits,  410. 
load  curves,  426,  428.                      Power  transmission,  433. 

low  head,  314.  air,  379. 

medium  heads,  309,  321.  belting,  splicing  of,  448. 

Niagara  Falls,  328.  cost,  380. 

reinforced  concrete,   310,   311,  couplings,  disc,  434. 

312.  efficiency,  486. 
steam,  boilers,  380.  diagram,  491. 

comparison  of   types,  tested,  492. 

381.  electric,  cost,  380. 
cost  of,  382.  cross-arms,  470. 

efficiency  of,  382.  efficiency,  486. 

feeding,  387.  entrance  to  buildings,  460. 

house,  386.  frequency,  486. 

operation,  cost,  382.  general  instructions,  485. 

overload  capacity, 387  insulator  pins,  471. 

plant  capacity,  385.  cost  of,  471. 

setting,     dimensions,  insulators,  cost  of,  473, 

383,  384.  474. 


510 


INDEX. 


Power    transmission,     electric,    in- 
sulators,   selection  of, 

471. 
line,  475. 

design  of,  476,  478. 

lightning   protection, 

'    484. 

loss,  478-484,  488. 

sag,  476. 
'    spacing  of,   478,  485. 

temperature,  effect  of, 
on  sag,  476. 

transposition,  478. 
pole  lines,  461. 

bracing  of,  469. 
pole  top,  design,  462. 
poles,  461. 

concrete-steel,  466. 

cost  of  467. 

strength  of,  467. 

life  of,  465. 

guying  of,  465. 

installation    of,     465, 
466. 

preservation  of,  464 . 

setting  of,  463-465. 

cost  of,   464. 

specifications  for,  461 

strains  on,  464. 
regulation,  486. 
towers,  467. 
voltages,  486. 
mechanical,  434. 
bearings,  445. 

babitting  of,  459. 

installation  of,  458. 
belting,  446. 

efficiency  of,  448. 

leather,  446. 

operation  of,  447. 

power  of,  448. 

rubber,  446. 

speeds  on,  448. 
clutches,  friction,  435. 
couplings,  434. 

design,  434. 

flexible,  435. 

jaw,  435. 
friction,  457. 
gears,  440. 

design  of,  440-444. 

strength  of,  442. 
keys,  436. 
quill,  shafts,  436. 
rope,  449. 

care  of,  455. 

centrifugal  force,  452. 

design,  452. 

efficiency,  450,  486. 

horse-power,  449. 


Power     transmission,      mechanical 
rope,  manilla  and    copper, 

449. 

sag,  449. 
sheaves,  454. 
steel,  453. 

steel,  design,  453-457. 
strength,  451. 
tension,  450. 
shafting,  436. 

design  of,  438,  439. 
efficiency,  487. 
friction,  457. 
worm  and  gear,  444. 
Power    in    unbalanced    two-phase 
circuits,   410. 

in  water,  curves,  49. 

measurement  of,  39. 
at  various  heads,  498. 
Pressure,  submerged  surface,  1. 
Prony  brakes,  368-371. 
capacity,  371. 
design  of,  370. 
shoes,  area,  370-371. 
Properties  of  various  sections,  116 
Puddle,  cost  of,  268. 

walls,  design  of,   186. 
Puentes  Dam,  profile  of,  239. 
Pulley  or  gear,  design,   135. 
Pumps. 

centrifugal,  179. 

adjustable  lining  for,  180. 
choice  of  motor  for,  181. 
horse-power  of,  180. 
operation  of,  182. 

QUILL  shafts.     See  Power  transmis- 
sion. 

RADIUS  of  gyration,   definition  of, 

113. 

Rainfall  data,  40. 
Ransom  bar,  reinforcement,  103. 
Reconnoissance  of  water  power,  39. 
Reinforcement,  103. 
Reinforcing  of  concrete,   102. 
Reports,  form  of,  65. 
engineer's,   62. 
government,  62. 

Reservoirs  in  connection  with  pen- 
stock, 349. 

relation  to  value  of  power,  45. 
Rivers,  flow  measurement,  33,  37. 
of  United  States,  run-off  and 

rainfall  data  for,  41,  42. 
Rock  work,  96. 
Roofs,  design  of,   165. 
Rope  drive.     See  Power  transmis- 
sion. 
Rosendale  cement,  70. 


INDEX. 


511 


Rotary  converter,  efficiency,  490. 
Run-off  data,  40. 

determined  without  run-off  re- 
port, 64. 
Safety  factors,  125. 

valves  for  high  pressure  pipe 
line,   366,   367. 

in  penstocks,  352. 

Sand  cement,  88. 

cost  of,  88. 
Sand,  seepage  through,  212. 

standardized,  77. 
Scott  system,  421. 
Screw  design,  130. 
Sections,  properties  of,   116. 
Shafting.    See  Power  transmission. 

alignment  of,  431. 

design,  129,  136. 
Sheet  piling.    See  Piling. 
Short  pipes,  flow  in,  29. 
Siphon,  6. 

operation  of,  7. 
Slag  cements,   100. 
Slope,  fall  in  feet  per  mile,  etc.,  28. 
Sluice  gates,  296. 

S.  Morgan  Smith  turbine  gate,  334. 
Soils,  angle  of  repose,   188. 

bearing  strength  of,  124. 
"  Soo  "  plant,  314. 
Soundings,  56. 

rock  bottom,  57. 

soft  bottom,  57. 
Speed    regulation,  throttling  gates, 

343. 
Standard  profile  for  masonrv  dam, 

258. 
Standpipe,  357. 

function  of,  365. 

ideal    arrangement    with    tur- 
bine unit,  363,  364. 
Steam  engines.    See  Power  plants, 
steam. 

plant.     See  Power  plants. 

cost  of,  51. 

Steel  piling.     See  Piling. 
Stones,  strength  of,  255. 

water    absorbed     by     various 

kinds,   240. 
Storage  battery,  421. 

boosters,  424. 

buckling,  425. 

capacity,  calculation  of,  427. 

charging  of,  423. 

cost  of,  428. 

cost  of  operation,  428. 

design,  423. 

design  for  central  station,  422. 

discharging,  423. 

efficiencies,  427. 

electrolyte,  425. 


Storage  battery,  end  cell  switch,  429 

end  cells,"  423. 

location  of,  429. 

operation,  425. 

rating  of,  423. 

reasons  for  using,  421. 

room  ventilation,  422. 

sulphate,  425. 
Straight  edge,  431. 
Stranded  cable,  reinforcement,  103. 
Strength  of  materials,  113. 

of  various  materials,  table,  115. 
Surveys,  cost  of,  61. 
Suspension  bridge,  design  of,  168. 
Susquehanna    River,    run-off    and 

rainfall  data,  41-44. 
Switches,  402. 

contact  surface,  403. 

design  of,  401,  402. 

high  tension,  403. 

oil,  404. 

voltmeter,  405. 

Switchboards.    See  Power  house. 
Svnchronous  converter,   efficiency, 
490. 

TABLES  and  formulas,  495. 
Tail  race,  design  of,  344. 

velocity,     permissible     during 

floods,   342. 
Tainton  gate,  350. 
Tapes,  steel,  433. 
Telephone  lines  on  a  transmission 

line,  477. 
Tent,  cost  of,  101. 
Test  holes,  56. 
Testing  of  turbines,  367. 
Throttling  gates,  343. 
Timber,  suitable  for  hydraulic  con- 
struction, 68. 

built  up,  166. 
Transformers,  415. 

air-blast,  data  of,  416.  . 

banking  of,  419. 

capacity  of,  420. 

connection  of,  420. 

connections,  Scott  system,  421. 

cooling  methods,  416. 

cost  of,  417. 

current,  407. 

data,  417. 

efficiency,  488,  489. 

oil,  417. 

phase  changers,  421. 

potential,  405. 

power  required  to  air  cool,  417. 

protection  of,   418. 

selection  of,  489. 

temperature,  416. 

water  required  to  cool,  417. 
Transpositions,  478. 


512 


INDEX. 


Truss  bridges,  design  of,  164. 

roofs,  design  of,  165. 
Tunnels,  blasting,  charges,  195. 
cost  of,  198. 
drilling  of,   193. 
earth,  195. 

cost  of  excavations,  198. 
rock,  192,  193. 

itemized  cost  of,  199. 
Turbine  chamber.  See  Flume.   344. 
setting,  "  Soo  "  plant,  316. 

special,  339. 
Turbines,  331. 

choice  of  capacity,  319. 
classification  of,  332. 
comparison  of  various  makes, 

321. 

efficiency,  331,  334,  487. 
gates,  333. 

energy  required  to   oper- 
ate,  355. 

time  required  to  close,  355 
governors,  353. 
harness,  445. 
high  pressure,  334,  348. 

setting  for,  314. 
horizontal,  335. 

efficiency,  337. 
Leffel,  333. 

old,  efficiency  of,  493,  494. 
regulation,  back  water  condi- 
tions, 340,  341. 

choice  of  gate,  360. 
cylinder    gate,    balancing 

of,  356. 

draft  tubes,  effect  on,  358. 
energy  required  to  operate 

gates,  357. 
energy  stored  in  fly-wheel, 

363. 

fly-wheels,  use  of,  358. 
governors,  358. 
high  head  system,  365. 
influence  of  plant  location 
on,  selection    of    gover- 
nor,  357. 

relation    between    stand- 
pipe  pressure,  fly-wheel 
and  regulation,  364. 
requirements  of  governor, 

361. 

set,  362. 
standpipe    with    damping 

pipe,   357. 
time     required     to     close 

gates,  355. 
wicket  gate,  balancing  of, 

356. 

relation  of  speed  to  size,  345. 
runners,  332. 
running  parts,  334. 


Turbines,  selection  of,  337. 
settings,  335. 

typical,  338. 
speed  of,  331. 
step  bearing,  346. 
testing  of,  367. 

equalizing  rack.  368. 

hook  gauge,  use  of,  368. 

wheel  pit,  weir,  367. 
vertical,  efficiency,   337. 
water  used  by,  331. 
wear,  335. 
wicket  gate,  356. 

UNITED  STATES  gallon,  1. 

Upper  Tallasee  Dam,  profile  of,  239. 

VACUUM,  experiments,  245. 
Vacuums,  action  of,  242. 

values  of,  244. 
Valves  used  with  centrifugal  pumps 

183. 
Velocity  of  approach,  4,  15. 

limits  of  air  in  pipes,  30. 
Venturi  meters,  18. 

as  head  gates,  19. 
Victor  turbine  runner,   332. 
Voltmeter.    See  Instruments. 


WASTE  gates,   296. 

hydraulically  operated,  297. 
umbrella  type,  296. 
Water,  1. 

flow  of,  3. 

orifice,  submerged,  4. 
through  circular  orifice,  3. 
through    rectangular    ori- 

fice, 3. 
hammer,  prevention  of,  349. 

relieve  of,  367. 
power,  measurement  of,  39. 
weight  of,  1. 
Waterwheels,  331. 
Watt  -hour  meters.  See  Instruments 
Wattmeters.   See  Instruments. 
Weirs,  10. 

submerged,  11. 
in  earth  dam,  271. 
for  wheel  pit,  367. 
table,  13. 

Winches,  design,  132. 
Wiring  formula  for  a.c.   and   d.c., 

481. 
Woods,  68. 

life  of,  465. 

suitable  for  construction,  68. 
Woodward  governor,  type  B,  355. 

types  C  and  D,  354. 
Worm  wheel.    See  Power  transmis- 


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